CN110380697A - Copped wave preamplifier and integrated circuit - Google Patents
Copped wave preamplifier and integrated circuit Download PDFInfo
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- CN110380697A CN110380697A CN201910691213.6A CN201910691213A CN110380697A CN 110380697 A CN110380697 A CN 110380697A CN 201910691213 A CN201910691213 A CN 201910691213A CN 110380697 A CN110380697 A CN 110380697A
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Classifications
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/32—Modifications of amplifiers to reduce non-linear distortion
- H03F1/3205—Modifications of amplifiers to reduce non-linear distortion in field-effect transistor amplifiers
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/32—Modifications of amplifiers to reduce non-linear distortion
- H03F1/3211—Modifications of amplifiers to reduce non-linear distortion in differential amplifiers
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/34—Negative-feedback-circuit arrangements with or without positive feedback
- H03F1/342—Negative-feedback-circuit arrangements with or without positive feedback in field-effect transistor amplifiers
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/38—DC amplifiers with modulator at input and demodulator at output; Modulators or demodulators specially adapted for use in such amplifiers
- H03F3/387—DC amplifiers with modulator at input and demodulator at output; Modulators or demodulators specially adapted for use in such amplifiers with semiconductor devices only
- H03F3/393—DC amplifiers with modulator at input and demodulator at output; Modulators or demodulators specially adapted for use in such amplifiers with semiconductor devices only with field-effect devices
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/45—Differential amplifiers
- H03F3/45071—Differential amplifiers with semiconductor devices only
- H03F3/45076—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier
- H03F3/45179—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier using MOSFET transistors as the active amplifying circuit
- H03F3/45183—Long tailed pairs
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Abstract
A kind of copped wave preamplifier and integrated circuit, including a pair of of chopping switch, and sequentially connected input buffer stage, gain amplification stage, output filtering stage, one of chopping switch is arranged before inputting buffer stage, another is arranged after inputting buffer stage, and chopping operational amplifier is used inside gain amplifying circuit, to which copped wave " dispersion " be changed, so that copped wave only handles small differential signal, avoid exchanging big differential signal back and forth, to avoid big state change.The recovery difficulty and recovery time which greatly simplifies signals after disturbed are very small for the loss of the integrality of signal.
Description
Technical field
The application belongs to CMOS integrated device technology field more particularly to a kind of copped wave preamplifier and integrated circuit.
Background technique
Wave chopping technology, which is briefly described, is: using a pair of of chopping switch, difference channel being placed in this between chopping switch.
This realizes chopping switch does not stop to exchange back and forth to differential signal with phase and reverse phase.It functionally sees, input side switch completes
To the modulation function (modulator) of input signal, and output side switch completes the demodulation function (de- to output signal
modulator).Final effect is: (frequency spectrum shift twice having occurred back and forth, but final without influence for signal spectrum
Return to origin), but for the noise for the difference channel being located between two chopping switch, due to only experienced primary solution
Tune process, therefore a frequency spectrum shift only has occurred, low frequency 1/f noise and imbalance have been shifted to high frequency treatment, finally subsequent
Low-pass filter filter out.Although wave chopping technology can eliminate imbalance and 1/f noise, due to introducing chopper clock, exist
Punctuated turning over and disturbance to precision analog circuits, therefore unavoidably introduce clock feedthrough, charge injection, signal quilt
Disturbance and the again non-ideal factors such as recovery.It, can the severe exacerbation linearity and gain essence if these problems processing is bad
Degree.
The currently used preamplifier architectures with copped wave function include: input buffer stage, gain amplification stage and defeated
Filtering stage out, chopping switch is generally located on gain amplification stage both ends or input side switch is arranged before inputting buffer stage
The rear end of gain amplification stage is arranged in end, output side switch.So that there are big signal, copped waves at output side switch chopping switch
Process causes very big state change, results in the integrity issue of signal, influences the linearity and gain accuracy.In addition, due to mesh
The input impedance of structure of preceding input buffer stage, technique require, gain accuracy and the problem of the linearity, so that putting before entire
The performance of big device is also affected
Summary of the invention
The application's is designed to provide a kind of copped wave preamplifier and integrated circuit, it is intended to solve currently used
There are, there are big signal, chopping process causes the very big state of signal to become at output side switch chopping switch for copped wave preamplifier
The problem of changing, will affect the integrality of signal, the linearity and gain accuracy.
The first aspect of the embodiment of the present application provides a kind of copped wave preamplifier, comprising:
First chopping switch, two input terminals of first chopping switch are respectively connected to two input signals, and described
One chopping switch is used to export to after the modulation of described two input signals；
Two of input buffer circuit, two input terminals of the input buffer circuit and first chopping switch are defeated
Outlet connection, the input buffer circuit use source follower structure, export after providing impedance isolation for the input signal；
Two input terminals of the second chopping switch, second chopping switch are separately connected the input buffer circuit
Two output ends, second chopping switch after the output signal of the input buffer circuit is mediated for exporting；
Two of gain amplifying circuit, two input terminals of the gain amplifying circuit and second chopping switch are defeated
Outlet connection, the gain amplifying circuit is using the chopping operational amplifier that can eliminate imbalance and noise, for it will reconcile after
The output gain signal amplification exports amplified signal after eliminating imbalance and noise；
Output filter circuit, the output end of two input terminals and the gain amplifying circuit of the output filter circuit
Connection, the output filter circuit are used to export to after amplified signal filtering.
The input buffer circuit includes two input buffer cells, each input in one of the embodiments,
Buffer cell includes first current source of the differential concatenation between power supply and common potential, being made of in the same direction or the first transistor
The first main source follower and the first auxiliary source follower for being made of at least one second transistor, the first transistor
The input terminal as the input buffer circuit is connect altogether with the grid of the second transistor, first current source and described
Output end of the total contact as the input buffer circuit between first main source follower, the first auxiliary source follower are used
In the channel-length modulation for eliminating the first main source follower.
The input buffer cell further includes the level for increasing output level displacement in one of the embodiments,
Shift module, in which:
The level shift module is connected between first current source and the first main source follower, the electricity
Output of the total contact as the input buffer cell between translational shifting module and first current source.
The level shift module is connected to the described first main source follower and described in one of the embodiments,
Between one auxiliary source follower.
The first transistor and the second transistor are PMOS tube in one of the embodiments, and described first is brilliant
The source electrode of body pipe connects power supply by first current source, is connected to institute after at least one described second transistor series aiding connection
It states between the drain electrode of the first transistor and common potential；Or
The first transistor and the second transistor are NMOS tube, and the source electrode of the first transistor passes through described
First current source connects common potential, is connected to the first transistor after at least one described second transistor series aiding connection
Between drain electrode and power supply.
The first transistor and the second transistor work in saturation region in one of the embodiments,；It is described
The threshold voltage of the first transistor is greater than the threshold voltage of the second transistor.
The threshold voltage of the first transistor is greater than the threshold value of the second transistor in one of the embodiments,
Voltage relationship are as follows: | Vth1 |-| Vth0 | >=| Vod0 |+margin；
Wherein, Vth1 is the threshold voltage of the first transistor, and Vth0 is the threshold voltage of the second transistor,
Vod0 is the overdrive voltage of the second transistor, and margin is voltage margin.
The gain amplifying circuit includes the first chopping operational amplifier, the second copped wave fortune in one of the embodiments,
Amplifier, the first sectional pressure element, the second sectional pressure element and third sectional pressure element are calculated, first chopping operational amplifier
First input end of the normal phase input end as the gain amplifying circuit, one end of first sectional pressure element and described first
The output end of chopping operational amplifier connects, the other end of first sectional pressure element and first chopping operational amplifier
Inverting input terminal, second sectional pressure element one end connection, the other end of second sectional pressure element cuts with described second
One end connection of the inverting input terminal of wave operational amplifier, the third sectional pressure element, second chopping operational amplifier
Second input terminal of the normal phase input end as the gain amplifying circuit, the other end of the third sectional pressure element and described the
The output end of two chopping operational amplifiers connects, and the output end of first chopping operational amplifier amplifies as the gain
First output end of circuit, the output end of second chopping operational amplifier are second defeated as the gain amplifying circuit
Outlet.
The output filter circuit includes first resistor, second resistance and filtered electrical in one of the embodiments,
Hold, one end of the first resistor, the second resistance one end respectively as two of output filter circuit inputs
End, the filter capacitor is serially connected between the other end of the first resistor and the other end of the second resistance, and described the
The other end of one resistance, the second resistance the other end respectively as the output filter circuit two output ends.
The second aspect of the embodiment of the present application provides a kind of integrated circuit, including the preposition amplification of copped wave as described above
Device.
Input buffer stage in above-mentioned copped wave preamplifier uses source follower structure, can greatly improve line
Property degree performance and gain accuracy performance, avoid input buffer stage from becoming the bottleneck of performance；It is defeated that copped wave is respectively acting on the first order
Inside the operational amplifier for entering buffer and second level gain amplification stage, so that copped wave is decentralized, copped wave only handles small
Differential signal, avoid exchanging big differential signal back and forth, to avoid big state change, which greatly simplifies signal quilts
Recovery difficulty and recovery time after disturbance are very small for the loss of the integrality of signal.
Detailed description of the invention
In order to more clearly explain the technical solutions in the embodiments of the present application, embodiment or the prior art will be retouched below
Attached drawing needed in stating is briefly described, it should be apparent that, the accompanying drawings in the following description is only the one of the application
A little embodiments for those of ordinary skill in the art without any creative labor, can also basis
These attached drawings obtain other attached drawings.
Fig. 1 is the structural schematic diagram of copped wave preamplifier provided by the embodiments of the present application；
Fig. 2 is the structural schematic diagram and circuit diagram of typical chopping switch；
Fig. 3 A and 3B are respectively the structural schematic diagram of two kinds of input buffer circuits in the copped wave preamplifier of Fig. 1；
Fig. 4 is the exemplary circuit schematic diagram of input buffer circuit embodiment one shown in Fig. 3 A；
Fig. 5 is the exemplary circuit schematic diagram of input buffer circuit embodiment two shown in Fig. 3 A；
Fig. 6 is the exemplary circuit schematic diagram of input buffer circuit embodiment three shown in Fig. 3 B；
Fig. 7 is the exemplary circuit schematic diagram of input buffer circuit example IV shown in Fig. 3 B；
Fig. 8 is the exemplary circuit schematic diagram of input buffer circuit embodiment five shown in Fig. 3 A；
Fig. 9 is the exemplary circuit schematic diagram of input buffer circuit embodiment six shown in Fig. 3 A；
Figure 10 is the circuit diagram of the source follower structure input buffer circuit that traditional single PMOS tube is constituted and its defeated
Enter/signal output waveform figure；
Figure 11 is the circuit diagram and its input/output signal waveform diagram of input buffer circuit shown in Fig. 4；
Figure 12 is the exemplary circuit schematic diagram of the first copped wave preamplifier provided by the embodiments of the present application；
Figure 13 is the exemplary circuit schematic diagram of second of copped wave preamplifier provided by the embodiments of the present application；
Figure 14 is the exemplary circuit schematic diagram of typical chopping operational amplifier.
Specific embodiment
In order to which the objects, technical solutions and advantages of the application are more clearly understood, with reference to the accompanying drawings and embodiments,
The application is further elaborated.It should be appreciated that specific embodiment described herein is only used to explain this Shen
Please, it is not used to limit the application.
Referring to Fig. 1, copped wave preamplifier provided by the embodiments of the present application can be used for integrated circuit.It is cut including first
Wave switch 01, input buffer circuit 02, the second chopping switch 03, gain amplifying circuit 04 and output filter circuit 05.
Two input terminals of the first chopping switch 01 are distinguished as two input terminals vin, vip of copped wave preamplifier
Two input signals are accessed, the first chopping switch 01 is used to after modulating two input signals export；Input buffer circuit 02
Two input terminals are connect with two output ends of the first chopping switch 01, and input buffer circuit 02 uses source follower structure, are
Input signal exports after providing impedance isolation；Two input terminals of the second chopping switch 03 are separately connected input buffer circuit 02
Two output ends vbf_n, vbf_p, the second chopping switch 03 is for being mediated the output signal of input buffer circuit 02
After export；04 two input terminals of gain amplifying circuit are connect with two output ends of the second chopping switch 03, gain amplifying circuit
04 using the chopping operational amplifier that can eliminate imbalance and noise, for amplifying and disappearing the output gain signal after reconciling
Except imbalance and noise after export amplified signal；The output end of output filter circuit 05 two input terminals and gain amplifying circuit 04
Vop_f, von_f connection, output filter circuit 05 are used to export to after amplified signal filtering.
The chopping scheme of above-mentioned copped wave preamplifier are as follows: for the input independent copped wave of buffer stage；For gain amplification stage
Copped wave is placed in the inside of amplifier, copped wave only is carried out to amplifier.This is just by copped wave localization, small range.By tradition defeated
" entirety " chopping scheme for entering the rear end setting of buffer stage front end and gain amplification stage disperses, multiple part chopping schemes, so that
Copped wave only handles small differential signal, avoids exchanging big differential signal back and forth, so that big state change is avoided, it is significantly simple
Changed signal it is disturbed after recovery difficulty and recovery time, it is very small for the loss of the integrality of signal.
Fig. 2 is the typical circuit figure of chopping switch, and the first chopping switch 01 and the second chopping switch 03 are identical, is distinguished
There are 4 ports, is successively denoted as a pair of of input terminal in+ and output end out+, another pair input terminal in- and output end out-, this two
It is full symmetric to port, without any difference.
Input buffer circuit 02 includes two input buffer cells 10, and each input buffer cell 10 includes series aiding connection
The first current source Iss between power Vcc and common potential Vss of (see Fig. 3 A) or differential concatenation (see Fig. 3 B), by the first crystalline substance
The first main source follower 100 that body pipe is constituted and the first auxiliary source follower 200 being made of at least one second transistor,
The grid of the first transistor and second transistor meets the input terminal as input buffer circuit 02, the first current source Iss and altogether
Input terminal of the total contact as input buffer circuit 02 between one main source follower 100, the first auxiliary source follower 200 are used for
Eliminate the channel-length modulation of the first main source follower 100.
This programme be the composition of single metal-oxide-semiconductor input buffer cell 10 on the basis of improve, the first main source follower 100 also
It is single transistor, the first auxiliary source follower 200 is single or multiple concatenated transistors.And the first current source Iss, first
Main source follower 100 and the first auxiliary source follower 200 are successively connected on power Vcc and common potential Vss forward or backwards
It is p-type or N type depending on transistor between (as greatly).Input buffer cell 10 constitutes two sources using different crystal pipe
Follower, one of to be used as main source follower, as auxiliary source follower, the effect of auxiliary source follower is to eliminate master for another
The channel-length modulation of source follower, to increase substantially the linearity and gain accuracy of preamplifier.
About the embodiment of input buffer cell 10, due to requiring two input buffer cells 10 identical, then not losing one
As property, by taking one of input buffer cell 10 as an example for:
Embodiment one:
Referring to Fig. 4, the first transistor and second transistor in input buffer cell 10 are PMOS tube, then first
Current source Iss, the first main source follower 100 and the first auxiliary source follower 200 are sequentially connected in series in power Vcc and common potential
Between Vss, the source electrode of the first transistor connects power Vcc by the first current source Iss, at least one second transistor is gone here and there in the same direction
It is connected to after connection between the drain electrode of the first transistor and common potential Vss.Specifically, the first transistor is PMOS tube PM1, the
Two-transistor is PMOS tube PM0, and the substrate of PMOS tube PM0 connects its source electrode, PMOS tube PM0 grounded drain；The lining of PMOS tube PM1
Bottom connects its source electrode, and the drain electrode of PMOS tube PM1 connects the source electrode of PMOS tube PM0.First current source Iss provides bias current, it is set to
Between power Vcc and the source electrode of PMOS tube PM1, bias current direction is to flow to PMOS tube PM1 from power Vcc.Input signal
Vin is applied on the input grid of PMOS tube PM0 and PMOS tube PM1 simultaneously, and output signal vbf_n is derived from PMOS tube PM1's
Source electrode.
Embodiment two:
Referring to Fig. 5, the input buffer cell 10 of the present embodiment is to expand to multiple PMOS on the basis of example 1
The cascaded structure of source follower, wherein the first transistor PMOS tube PM1 constitutes " master " source follower, remaining second transistor
PMOS tube PM_a0~PM_an constitutes the first auxiliary source follower 200, PMOS tube PM1 and PMOS tube PM_a0~PM_an together
Grid connect the input as preamplifier altogether, output signal vbf_n is derived from the PMOS tube of the output as preamplifier
The source electrode of PM1.
Embodiment three:
Referring to Fig. 6, the first transistor and second transistor of input buffer cell 10 are NMOS tube, then first is auxiliary
Source follower 200, the first main source follower 100 and the first current source Iss are sequentially connected in series in power Vcc and common potential Vss
Between, the source electrode of the first transistor meets common potential Vss by the first current source Iss, at least one second transistor is gone here and there in the same direction
It is connected between the drain electrode of the first transistor and power Vcc after connection.Specifically, the first transistor is NMOS tube NM1, and second is brilliant
Body pipe NMOS tube NM0, the substrate of NMOS tube NM0 connect its source electrode, and NMOS tube NM0 drain electrode connects power Vcc；The substrate of NMOS tube NM1
Its source electrode is connect, the drain electrode of NMOS tube NM1 connects the source electrode of NMOS tube NM0.First current source Iss provides bias current, it is placed in
Between common potential Vss and the source electrode of NMOS tube NM1, bias current direction is that NMOS tube NM1 flow direction public affairs are flowed to from power Vcc
Common-battery position Vss.Input signal vin is applied on the input grid of NMOS tube NM0 and NMOS tube NM1 simultaneously, output signal
Vbf_n is derived from the source electrode of NMOS tube NM1.In the present embodiment, the cascaded structure constituted using 2 NMOS source followers, with implementation
2 PMOS tube structure perfect dualities of example one.This when, the common mode electrical level of input signal vin can be very high, such as directly takes
Supply voltage.
Example IV:
Referring to Fig. 7, the input buffer cell 10 of the present embodiment is to expand to multiple NMOS on the basis of embodiment three
The cascaded structure of source follower, wherein the first transistor NMOS tube NM1 constitutes " master " source follower, remaining second transistor
NMOS tube NM_a0~NM_an constitutes the first auxiliary source follower 200, NMOS tube NM1 and NMOS tube NM_a0~NM_an together
Grid connect the input as preamplifier altogether, output signal vbf_n is derived from the NMOS tube of the output as preamplifier
The source electrode of NM1.The cascaded structure of multiple NMOS source followers of the present embodiment is followed with multiple sources PMOS in embodiment two
The cascaded structure perfect duality of device.
Embodiment five:
Referring to Fig. 8, the input buffer cell 10 of the present embodiment be embodiment one to four any one on the basis of expand
Open up the structure for increasing a DC level shift module 300.In the present embodiment, level shift module 300 is connected to the first electricity
Between the main source follower 100 of stream source Iss and first, the total contact between level shift module 300 and the first current source Iss is made
For the output of preamplifier, level shift module 300 is for increasing output level displacement.Wherein, main, the first auxiliary source follows
Device 200 is not limited to PMOS tube or NMOS pipe, the metal-oxide-semiconductor quantity of the first auxiliary source follower 200 are also unlimited.
In example shown in Fig. 8, DC level shift module 300 is resistance R0, is serially connected in output and follows with the first main source
Between the PMOS tube PM1 of device, be able to solve depend merely on PMOS tube PM1 pipe can make output level displacement not enough, this when increases
Level shift module 300 can further increase DC level displacement, while not influence signal quality.Sometimes, in order to allow
The gain amplifying circuit 04 of second level works at comfortable bias voltage vbias, this level shift module 300 is necessary.
In other embodiments, resistance R0 could alternatively be a circuit module, regardless of the specific implementation of this circuit module, only
The function of wanting it is to increase DC level displacement, while not influencing signal quality, then being exactly the protection model for belonging to this programme
It encloses.
Embodiment six:
Referring to Fig. 9, the input buffer cell 10 of the present embodiment be embodiment one to four any one on the basis of expand
Open up the structure for increasing a DC level shift module 400.In the present embodiment, it is main that level shift module 400 is connected to first
Between source follower 100 and the first auxiliary source follower 200, level shift module 400 is for increasing output level displacement.Wherein,
Main, the first auxiliary source follower 200 is not limited to PMOS tube or NMOS tube, and the metal-oxide-semiconductor quantity of the first auxiliary source follower 200 is also unlimited.
In addition, the scheme in the present embodiment can be applied in combination with the scheme of embodiment five.
In example shown in Fig. 9, DC level shift module 400 is resistance R1, is serially connected in the first main source follower 100
The auxiliary source follower 200 of PMOS tube PM1 and first PMOS tube PM0 between.It is able to solve and depends merely on PMOS tube PM1 pipe and can make
Not enough, DC level displacement can be further increased by increasing level shift module 400 this when, simultaneously for output level displacement
Do not influence signal quality.In other embodiments, resistance could alternatively be a circuit module, regardless of this circuit module
Specific implementation while not influencing signal quality as long as its function is to increase DC level displacement, then being exactly to belong to this
The protection scope of scheme.
It is and right although Fig. 8,9 being illustrated by taking 2 grades of MOS source follower cascaded structures as an example it must be noted that as above-mentioned
Be in multistage MOS source follower cascaded structure it is applicable, in these structures be inserted into level shift module, belong to protect
Range.
Please continue to refer to Fig. 4, below by in input buffer cell 10 the first transistor and second transistor be PMOS
Pipe, and the first auxiliary source follower 200 be a PMOS tube for illustrate relative theory.Specifically, the core of preamplifier
Divide and uses 2 PMOS tube PM0 and PM1 and first current source Iss.Therefore structurally, the two PMOS tube
PM0 and PM1 is to constitute source follower, but its input is connected in parallel, and output " series connection " is together.PMOS tube PM1 is constituted
Main source follower, PMOS tube PM0 constitute auxiliary source follower；The presence of PMOS tube PM0 has carried out at linearisation PMOS tube PM1
Reason, so that the linearity of PMOS tube PM1 greatly improves, and output signal vbuffer is exactly generated by PMOS tube PM1.Exactly by
In this cleverly connection relationship, just the linearity is greatly improved, gain accuracy greatly improves, and other aspects performance
(such as consumption of output impedance, noise, power consumption, voltage margin) is suitable with common single PMOS tube source follower.This is in simulation electricity
It is very rare phenomenon in the design field of road, because being filled with various compromises in Analog Circuit Design field
(tradeoff), usually a kind of circuit framework compares another kind in terms of certain when excellent performance, often to sacrifice other aspects
It can be what cost was brought.
In Fig. 4 structure, PMOS tube PM0 and PMOS tube PM1 need fine design and choose size, to guarantee to allow 2
MOS works in saturation region, and this is that effective basic demand is answered in the performance of this structure.PMOS tube PM0 work is allowed to be saturated
Area's very comfortable, difficult point be that PMOS tube PM1 is allowed to work in saturation region, it must satisfy:
|Vds1|≥(|Vgs1|-|Vth1|)+margin
Wherein, Vds1, Vgs1, Vth1, margin are respectively drain-source voltage, gate source voltage, the threshold value electricity of PMOS tube PM1
In general pressure, voltage margin, margin take 100~200mV or so.Assuming that the common mode electrical level of input signal vin is 0, above formula
Further it is written as:
vbf_n-vt≥vbf_n-|Vth1|+margin
Further are as follows:
|Vth1|≥Vt+margin
Due to vt=| Vgs0 |=| Vth0 |+Vod0, vt are that the drain electrode of PMOS tube PM1 and the source electrode of PMOS tube PM0 are total to contact
Voltage, Vgs0, Vth0, Vod0 are gate source voltage, threshold voltage, the overdrive voltage of PMOS tube PM0,
Therefore, above formula is further written as:
|Vth1|-|Vth0|≥Vod0+margin≈Vod0+100mV
This means that the threshold voltage of PMOS tube PM1 must be Vod0+margin bigger than the threshold voltage of PMOS tube PM0, i.e.,
At least in 100mV or more.In order to realize this target, at least 2 kinds of feasible solutions:
The first: technique can generally provide the option of a variety of threshold mos pipes.Can choose PM1 is high threshold pipe metal-oxide-semiconductor,
PM0 is Low threshold pipe metal-oxide-semiconductor, this can easily realize target.
Second: passing through fine and cleverly size design realization.Allow PMOS tube PM0 W/L (W be conducting channel width
Degree, L are the length of conducting channel) it is sufficiently large, make its work in subthreshold region, at this moment Vod0 can be very small (such as 50mV).
Allow the L of PMOS tube PM0 that the minimum length under current process is taken (such as 0.35um CMOS technology, to take L=simultaneously
0.35um), and the minimum usually band of L has also carried out lesser threshold voltage.In addition, making the W/L of PMOS tube PM1 as small as possible, simultaneously
L takes (such as 0.35um CMOS technology, taking L=4um) as big as possible under current process, the Vod1 of such PMOS pipe PM1
Sufficiently large, the channel-length modulation of itself is sufficiently small, and the linearity is also as well as possible.And the biggish L of PMOS tube PM1 is usual
Also biggish threshold voltage is brought.Like this, by allowing | Vth1 | it is as big as possible, allow | Vth0 | it is as small as possible, make Vod0 most
May be small, so that above formula meets, this programme structure bring effect is then played, has further made the linearity more preferable.
Next further analysis, why the proposed structure of this programme can increase substantially the linearity and gain essence
Exactness needs to investigate this problem by comparative analysis.
Figure 10 is the input buffer cell 10 for the source follower structure that traditional single PMOS tube is constituted, and substrate connects source electrode.Its
It is input to the gain of output are as follows:
Wherein gm is the mutual conductance of PMOS tube PM1, and gds is the intrinsic admittance of output of PMOS tube PM1.Gm/gds is known as metal-oxide-semiconductor
Intrinsic gain, this usual value is 100 or so, that is to say, that gds ≈ gm/100 usually can be ignored compared to gm, because
This Av is approximately equal to 1.If for the occasion of high-precision and high linearity, the influence of gds cannot be had ignored.Gds influences characterization
Be channel-length modulation, in this structure, gds determines the precision and the linearity of gain completely.Notice gds
Definition:
Therefore gds is the function of vds (drain-source voltage of metal-oxide-semiconductor).For the source follower of Fig. 8, due to vds=
Vbf_n-0 ≈ vin, so while the influence of gds, gain A v is actually still the minorant of input signal:
Here it is non-linear, then harmonic distortion is just produced.Design and simulation result are aobvious on typical CMOS processes
Show, 10,2 subharmonic of input buffer cell for the source follower structure that this traditional single PMOS tube is constituted and point of 3 subharmonic
Amount is difficult lower than < -80dBc, this means that the measurement based on this single PMOS tube source follower structure input buffer cell 10
System, number of significant digit (precision index is defined as ENOB=(SNDR-1.76)/6.02) is at most in 13bits or so, and this is right
It is far from being enough for high-precision applications occasion.
By the analysis to Figure 10, it is understood that bottleneck is gds.It is proposed that patent formula be exactly it is almost complete
It totally disappeared the influence in addition to gds.
As shown in figure 11, input signal vin generates vbf_n and vt by 2 source followers respectively.We are PMOS tube
PM1 is known as the first main source follower 100, and PMOS tube PM0 is known as the first auxiliary source follower 200.Vbf_n and vt are nearly all accurate
Equal to input signal vin, the magnitude of error is exactly harmonic component (in a ten thousandth of -80dBc or so, that is, signal itself
Left and right).
It is further noted that PMOS tube PM1,
Vds=vbf_n-vt ≈ vin+o (vin)-[vin+o (vin)]=o (vin) ≈ 0
Mathematically mark is employed herein, small o indicates " being much smaller than ", such as o (vin) indicates the amount for being much smaller than vin.Cause
This, the source electrode and drain electrode of PMOS tube PM1 is to synchronize to follow input wobble signal, but for its difference, almost 0 (is fluctuated
It is exactly a ten thousandth or so in input signal), therefore the variation of imperceptible vds.Since the variation of imperceptible vds, that
The gds of PMOS tube PM1 pipe is also just no better than 0.Therefore, for the circuit structure of the application:
Nonlinear component substantially reduces, therefore significantly reduces harmonic distortion.It is designed in same CMOS technology and imitative
Very the results show that using 10,2 subharmonic of input buffer cell for the new source follower structure of the application proposed and 3 times
The component of harmonic wave can accomplish < -120dBc, it is meant that the measuring system of the input buffer cell 10 based on this source follower,
Number of significant digit highest can achieve the level close to 20bits, and for high-precision applications occasion, enough (usual 16bits is left
It is right relatively common).
On the other hand the index to be considered is gain accuracy, this is equally to Guan Chong for high precision measuring system
It wants.In practice, every level-one in signal processing link (buffering isolation, amplification, filtering, analog-to-digital conversion ...) can all introduce increasing
Benefit, and the gain of every level-one can all be influenced by PVT (process deviation, power-supply fluctuation, temperature), often it is extremely complex even
It is difficult to accurately portray.In the influence of PVT:
The influence of usual power-supply fluctuation V can be by being designed to deal with, such as is placed in LDO (Low Dropout
Regulator, low pressure difference linear voltage regulator) under allow V to keep constant.
The influence of usual process deviation P is solved by the calibration link before chip/complete machine factory.So-called calibration is exactly
Yield value Av0 before chip/complete machine factory is write down, is stored in the nonvolatile memory of chip, referred to as demarcates.Normally
In use, being calibrated with Av0 to actual gain Av.In this way, the process variations between piece and piece are eliminated；
And the influence of temperature T, it must be become pair by outstanding design level and cleverly circuit structure by the gain of circuit
Temperature-insensitive.
For the source follower structure input buffer cell 10 that traditional single PMOS tube shown in Fig. 8 is constituted, increase
Benefit are as follows:
Wherein
Gds (PVT) and gm (PVT) be all with high temperature change amount, DEG C range from -40 DEG C to+85, gds (PVT)/
Gm (PVT) variable quantity is often as high as 2 times or more.As before, the representative value of gds/gm is about 1%, Av representative value and is about
0.99；But if Av variation with temperature is up to 1% or more in view of after the varying with temperature of gds/gm, this results in very big
Measurement error so that high precision measuring system becomes no longer accurate.Since gds (PVT)/gm (PVT) not only has relationship with T,
Also there is relationship with P, it means that for each chips, gds (PVT)/gm (PVT) temperature curve may be all different, makes
It must consider that the idea for doing temperature-compensating becomes not implementable and (needs to do temperature-compensating to each, cost is extremely expensive
).
But for the patent formula that the application proposes, gain are as follows:
Wherein
Assuming that the value of x itself is about 1%, variation is also about 1% within the scope of total temperature.As before, o (x) is one
The amount of 40dB also smaller than x or so (about 100 times), therefore the value of o (x) itself is about 0.01%, and become within the scope of total temperature
Change is also about 0.01% magnitude, is converted to about 8ppm/ DEG C of temperature coefficient, in terms of the document that can be found at present, this
Belong to most top level, meets the application of most high precision measuring systems.
The source follower that the application constitutes 2 metal-oxide-semiconductors, input terminal are connected in parallel, and output end " series connection " is together.
For one of metal-oxide-semiconductor as the first main source follower 100, another or multiple MOS pipes are defeated as the first auxiliary source follower 200
It is derived from the first main source follower 100 out.The effect of first auxiliary source follower 200 is the channel for eliminating the first main source follower 100
The effect of the length, to increase substantially the linearity and gain accuracy of input buffer cell 10.
In order to allow the metal-oxide-semiconductor of main, the first auxiliary source follower 200 all to work in saturation region, the design method of use: one
It is the design method using multi-threshold pipe；The second is using the pipe sizing choosing method more rich in skill.Both methods
It has a detailed description in front.
The input buffer cell 10 of the application and integrated circuit linearity degree are fabulous, and gain is extremely accurate；Input signal is not required to
Additional bias voltage vbias (sensor can be used as common-mode signal with directly taking) is provided；Circuit is extremely simple, and with
CMOS technology is completely compatible, is not necessarily to particular device；Impedance isolation (input is high impedance, is exported as Low ESR)；Other aspects
Energy (such as consumption of noise, power consumption, voltage margin) is suitable with common single metal-oxide-semiconductor source follower structure.This is in circuit design field
In be very rare phenomenon.In circuit design field, it is filled with various compromises (tradeoff), a kind of circuit framework ratio
Another kind excellent performance in terms of certain is often brought using sacrificing other aspects performance as cost.
Figure 12 and Figure 13 are please referred to, gain amplifying circuit 04 includes that the first copped wave operation is put in one of the embodiments,
Big device A0, the second chopping operational amplifier A0_, the first sectional pressure element R21, the second sectional pressure element R22 and third sectional pressure element
R23, first input end of the normal phase input end of the first chopping operational amplifier A0 as gain amplifying circuit 04, the first partial pressure
One end of element R21 is connect with the output end of the first chopping operational amplifier A0, the other end of the first sectional pressure element R21 and
One end connection of the inverting input terminal of one chopping operational amplifier A0, the second sectional pressure element R22, the second sectional pressure element R22's is another
One end is connect with one end of the inverting input terminal of the second chopping operational amplifier A0_, third sectional pressure element R23, the second copped wave
Second input terminal of the normal phase input end of operational amplifier A0_ as gain amplifying circuit 04, third sectional pressure element R23's is another
One end is connect with the output end of the second chopping operational amplifier A0_, and the output end of the first chopping operational amplifier A0 is as gain
First output end von of amplifying circuit 04, the output end of the second chopping operational amplifier A0_ is as gain amplifying circuit 04
Second output terminal vop.
Figure 12 and Figure 13 are please referred to, output filter circuit 05 includes first resistor Rf, the in one of the embodiments,
Two resistance Rf_ and filter capacitor, one end of first resistor Rf, second resistance Rf_ one end respectively as output filter circuit
05 two input terminals, filter capacitor Cf be serially connected in the first resistor Rf the other end and the second resistance Rf_ it is another
Between end, and the other end of the other end of first resistor Rf, the second resistance Rf_ are respectively as output filter circuit 05
Two output ends, i.e., as two outputs vop_f, von_f of copped wave preamplifier.
In the present embodiment, copped wave difference preamplifier is the difference knot constituted on the basis of Fig. 4 related embodiment
Structure, difference channel have symmetry, innately have rejection ability to even-order harmonic, therefore have more extensive use, practical
Most amplifier circuits are that occur in the form of difference (or pseudo-differential) in.
It must be noted that although two input buffer cells 10 of above-mentioned copped wave difference preamplifier are with 2 grades of PMOS
Illustrate for cascaded structure, in practice for all structures of including but not limited to embodiment one to six, may be constructed difference
Circuit, these belong to the protection scope of the application.In addition, the sectional pressure element can be resistance, capacitor, inductance, crystal
The passive circuit of at least one composition such as pipe.
It functionally sees, the first chopping switch 01 completes the modulation function to input signal vip, vin, and second cuts
Wave switch 03 completes the demodulation function of output signal vbf_p, vbf_n to input buffer circuit 02.Final effect is,
Without influence (from vip, vin → vbf_p, vbf_n) for signal, but to positioned at the first chopping switch 01, the second copped wave
For the noise of Differential Input buffer circuit 02 between switch 03, due to only experienced a demodulating process, have occurred
Frequency spectrum shift, low frequency 1/f noise have been shifted to high frequency treatment, are finally filtered out by the filter of rear class.
Gain amplifying circuit 04 is made of two amplifiers (A0 and A0_) and 3 sectional pressure elements (R21, R22 and R23),
Middle A0 and A0_ is identical amplifier, and gain amplifying circuit 04 is also full symmetric differential configuration.In amplifier A0 and A0_
Portion carries copped wave function, and Figure 14 gives a kind of copped wave embodiment of typical Differential Input Single-end output type amplifier.Output
Filter circuit 05 is mainly the high-frequency noise of filtering circuit, and cutoff frequency is much higher than signal frequency, therefore for signal
It is all-pass (in signal band, gain 1).
It is about input buffer stage that one of the application, which improves, another improvement is the improvement about chopping scheme.
It inputs buffer stage and uses a kind of very special structure, be a kind of high input impedance, linearity enhancing, gain
Accurate source follower structure.And other aspects performance (such as consumption of output impedance, noise, power consumption, voltage margin) and common
Single metal-oxide-semiconductor source follower is suitable.
The gain of entire copped wave preamplifier are as follows:
By the ratio for changing R21, R22 and R23, it can realize desired gain.
Second level gain stage due to use amplifier closed loop feedback form, as long as the open-loop gain of amplifier do it is enough
Height, then the linearity of gain stage and gain accuracy can do it is very good.
The application uses this input buffer circuit structure, and the linearity and gain accuracy is greatly improved.In allusion quotation
Design and simulation result are shown in type CMOS technology, the source follower structure input buffer that traditional single metal-oxide-semiconductor is constituted, 2 times
The component of harmonic wave and 3 subharmonic is difficult < -80dBc, and the variation of gain with temperature is up to ± 1%, this is for high-precision applications field
It is far from being enough for conjunction.And this input buffer structure in the application is used, point of 2 subharmonic and 3 subharmonic
Amount can accomplish < -120dBc, and the variation of gain with temperature is enough for most High Definition Systems down to ± 0.01%
?.Most of all, this is realized in pure CMOS technology, it is not necessarily to any particular device, without expensive BiCMOS technique
Support.
For input buffer stage, copped wave is placed in it and outputs and inputs.Since input buffering stage gain is 1, to signal
Do not amplify, therefore what is handled at the first chopping switch 01, the second chopping switch 03 is small differential signal, caused disturbs
Dynamic and recovery time is all very small, also very small for the loss of the integrality of signal.
For gain amplification stage, copped wave is placed in the inside of amplifier.Copped wave is the input and current signal positioned at amplifier
Differential path on.It is well known that differential signal handled by amplifier is very small when amplifier works in closed loop states
Error signal, therefore in the chopping switch of amplifier internal work, caused disturbance is minimum, to the integrity loss of signal
It is minimum.
Stage gain amplifying stage, copped wave are placed in the inside of 2 amplifiers, are equivalent to and have only done copped wave to amplifier, to sectional pressure element
Do not do copped wave.If there are mismatch or 1/f noises for sectional pressure element, it will directly be presented on output.And if sectional pressure element selects
With passive device, 1/f noise is not present；By rationally designing, matching precision can be extremely high.
Actual design test result shows, the scheme proposed using the application, the 1/f of entire copped wave preamplifier
Noise break frequency can be down to < 1Hz, imbalance < 10uV.If cooperating high-level system-level copped wave again, imbalance can be into one
Step is reduced to < 1uV.Due to significantly reducing the loss of signal integrity caused by copped wave, and cooperation high linearity input buffering
The use of device, 2 subharmonic of entire copped wave preamplifier and the component of 3 subharmonic can accomplish < -120dBc, and gain is with temperature
The variation of degree has high-precision attribute down to ± 0.01%.
The foregoing is merely the preferred embodiments of the application, not to limit the application, all essences in the application
Made any modifications, equivalent replacements, and improvements etc., should be included within the scope of protection of this application within mind and principle.
Claims (10)
1. a kind of copped wave preamplifier characterized by comprising
First chopping switch, two input terminals of first chopping switch are respectively connected to two input signals, and described first cuts
Wave switch after modulating to described two input signals for exporting；
Input buffer circuit, two input terminals of the input buffer circuit and two output ends of first chopping switch connect
It connects, the input buffer circuit uses source follower structure, exports after providing impedance isolation for the input signal；
Second chopping switch, two input terminals of second chopping switch be separately connected the input buffer circuit two are defeated
Outlet, second chopping switch after the output signal of the input buffer circuit is mediated for exporting；
Gain amplifying circuit, two input terminals of the gain amplifying circuit and two output ends of second chopping switch connect
It connects, the gain amplifying circuit is using the chopping operational amplifier that can eliminate imbalance and noise, for described defeated after reconciling
Amplified signal is exported after signal gain amplification, elimination imbalance and noise out；
Two input terminals of output filter circuit, the output filter circuit are connect with the output end of the gain amplifying circuit,
The output filter circuit is used to export to after amplified signal filtering.
2. copped wave preamplifier as described in claim 1, which is characterized in that the input buffer circuit includes two inputs
Buffer cell, each input buffer cell include first electric current of the in the same direction or differential concatenation between power supply and common potential
Source, the first main source follower being made of the first transistor and the first auxiliary source being made of at least one second transistor follow
The grid of device, the first transistor and the second transistor connects the input terminal as the input buffer circuit altogether, described
Output end of the total contact as the input buffer circuit between first current source and the first main source follower, described
One auxiliary source follower is used to eliminate the channel-length modulation of the described first main source follower.
3. copped wave preamplifier as claimed in claim 2, which is characterized in that the input buffer cell further includes for increasing
The level shift module for adding output level to shift, in which:
The level shift module is connected between first current source and the first main source follower, the level shift
Output of the total contact as the input buffer cell between module and first current source.
4. copped wave preamplifier as claimed in claim 2, which is characterized in that the level shift module is connected to described
Between one main source follower and the first auxiliary source follower.
5. copped wave preamplifier as claimed in claim 2, which is characterized in that the first transistor and second crystal
Pipe is PMOS tube, and the source electrode of the first transistor connects power supply by first current source, at least one described second crystal
It is connected to after pipe series aiding connection between the drain electrode and common potential of the first transistor；Or
The first transistor and the second transistor are NMOS tube, and the source electrode of the first transistor passes through first electricity
Stream source connects common potential, and drain electrode and the electricity of the first transistor are connected to after at least one described second transistor series aiding connection
Between source.
6. such as the described in any item copped wave preamplifiers of claim 2 to 5, which is characterized in that the first transistor and institute
Second transistor is stated to work in saturation region；The threshold voltage of the first transistor is greater than the threshold value electricity of the second transistor
Pressure.
7. copped wave preamplifier as claimed in claim 6, which is characterized in that the threshold voltage of the first transistor is greater than
The threshold voltage relationship of the second transistor are as follows: | Vth1 |-| Vth0 | >=| Vod0 |+margin；
Wherein, Vth1 is the threshold voltage of the first transistor, and Vth0 is the threshold voltage of the second transistor, and Vod0 is
The overdrive voltage of the second transistor, margin are voltage margin.
8. copped wave preamplifier as described in claim 1, which is characterized in that the gain amplifying circuit includes the first copped wave
Operational amplifier, the second chopping operational amplifier, the first sectional pressure element, the second sectional pressure element and third sectional pressure element, it is described
First input end of the normal phase input end of first chopping operational amplifier as the gain amplifying circuit, the first partial pressure member
One end of part is connect with the output end of first chopping operational amplifier, the other end of first sectional pressure element and described the
The inverting input terminal of one chopping operational amplifier, second sectional pressure element one end connection, second sectional pressure element it is another
One end is connect with one end of the inverting input terminal of second chopping operational amplifier, the third sectional pressure element, and described second
Second input terminal of the normal phase input end of chopping operational amplifier as the gain amplifying circuit, the third sectional pressure element
The other end is connect with the output end of second chopping operational amplifier, the output end conduct of first chopping operational amplifier
The output end of first output end of the gain amplifying circuit, second chopping operational amplifier amplifies electricity as the gain
The second output terminal on road.
9. copped wave preamplifier as described in claim 1, which is characterized in that the output filter circuit includes the first electricity
Resistance, second resistance and filter capacitor, one end of the first resistor, the second resistance one end respectively as the output
Two input terminals of filter circuit, the filter capacitor be serially connected in the first resistor the other end and the second resistance it is another
Between one end, and the other end of the other end of the first resistor, the second resistance is respectively as the output filter circuit
Two output ends.
10. a kind of integrated circuit, which is characterized in that including copped wave preamplifier as described in any one of claim 1 to 9.
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| CN112383353A (en) * | 2020-10-09 | 2021-02-19 | 淮阴师范学院 | Signal loss detection circuit |
| CN113552400A (en) * | 2020-04-23 | 2021-10-26 | 思睿逻辑国际半导体有限公司 | Current sensing circuit |
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