CN102104367A - Variable gain amplifier (VGA) - Google Patents
Variable gain amplifier (VGA) Download PDFInfo
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- CN102104367A CN102104367A CN2011100534768A CN201110053476A CN102104367A CN 102104367 A CN102104367 A CN 102104367A CN 2011100534768 A CN2011100534768 A CN 2011100534768A CN 201110053476 A CN201110053476 A CN 201110053476A CN 102104367 A CN102104367 A CN 102104367A
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Abstract
The invention provides a variable gain amplifier (VGA), which comprises a difference channel, wherein the difference channel is composed of a first load circuit, a second load circuit, a source degeneration circuit, a first emitter follower circuit and a second emitter follower circuit; a grid electrode or a base electrode of the first emitter follower circuit is connected with a forward voltage input end of the difference channel; a drain electrode or a collector electrode of the first emitter follower circuit is connected with the first load circuit; a grid electrode or a base electrode of the second emitter follower circuit is connected with a negative voltage input end of the difference channel; a drain electrode or a collector electrode of the second emitter follower circuit is connected with the second load circuit; and source electrodes or emitting electrodes of the two emitter follower circuits are respectively connected with the two ends of the source degeneration circuit. The emitter follower circuits are used in the VGA, and the VGA is simple in circuit structure, small in circuit area, and high in circuit linearity.
Description
Technical field
The present invention relates to the amplifier technology, relate in particular to a kind of variable gain amplifier.
Background technology
In wireless receiver, the signal strength signal intensity that antenna receives may alter a great deal, and receiver all must correctly demodulation for the signal of these varying strengths.For example, for global system for mobile communications (GSM) mobile phone, its the most weak received useful signal is-102dBm, the strongest received useful signal is-15dBm, the energy changing scope of signal is 87dBm, this is a very wide scope, and the receiver of any constant-gain is the correct signal of the so wide energy range of demodulation all.For the strong and weak different signal of correct demodulation, the gain of wireless receiver must automatically adjust according to signal strength signal intensity, make receiver when receiving weak signal, have very high gain, and when receiving strong signal, having lower gain, this is to be realized by the automatic gain control loop (AGC) that is core with variable gain amplifier (VGA).Along with the development of Digital Signal Processing, increasing receiver adopts digital signal to control the gain of variable gain amplifier.As shown in Figure 1, the output signal of VGA is transformed to digital signal through A-D converter, at numeric field the signal power is judged, and is provided the gain that the digital gain control word is controlled VGA.
Weigh one of the radio circuit performance very important parameters be the linearity, it has explained radio circuit owing to the non-linear distortion level of introducing, its value has determined the maximum input signal power that radio circuit can bear.For variable gain amplifier, high more its manageable maximum signal of the linearity is just big more.
For the open loop amplifier, its gain is the product of equivalence input mutual conductance Gm and equivalent output resistance Rout, and therefore, the mutual conductance that changes input stage just can change Amplifier Gain, constitutes the VGA based on the programmable trans-conductance amplifier.The mutual conductance of input stage is regulated and can be realized by bias current that changes input stage or the resistance that changes the source degeneracy resistance of input stage.
Fig. 2 has provided a kind of VGA based on the programmable trans-conductance device, and it is the differential amplifier that a resistance is done load, the mutual conductance that comes resonance-amplifier by the bias current that changes differential pair.By the square-law I-V characteristic of long channel device as can be known: the mutual conductance of differential pair is proportional to the square root of tail current source size of current, and therefore, the size that changes tail current source Iss just can change the mutual conductance of differential pair M1, M2.There is the problem of the linear work district narrow range of differential pair in such VGA.Fig. 3 has provided another kind of VGA based on the programmable trans-conductance device, the mutual conductance that it comes resonance-amplifier by the resistance that changes the input stage source degeneracy resistance R E in the degeneracy circuit of source, use source degeneracy technology can improve the linearity of trsanscondutor, but the linearity after improving is still not high, and it can reduce the mutual conductance of trsanscondutor, and the gain variation range of VGA is very little.
Summary of the invention
In order to solve the problems of the technologies described above, the present invention proposes a kind of variable gain amplifier, to have high linearity.
The present invention proposes a kind of variable gain amplifier, this variable gain amplifier comprises difference channel, described difference channel comprises first load circuit, second load circuit and source degeneracy circuit, described difference channel also comprises the first emitter follower circuit and the second emitter follower circuit, wherein, the grid of the described first emitter follower circuit or base stage link to each other with the forward voltage input of described difference channel, and drain electrode or collector electrode link to each other with described first load circuit; The grid of the described second emitter follower circuit or base stage link to each other with the negative voltage input of described difference channel, and drain electrode or collector electrode link to each other with described second load circuit; The source electrode of described two emitter follower circuit or emitter are connected respectively to the two ends of described source degeneracy circuit.
Preferably, above-mentioned variable gain amplifier can have following characteristics:
The described first emitter follower circuit comprises first operational amplifier and metal-oxide semiconductor (MOS) (MOS) pipe, and the in-phase input end of described first operational amplifier links to each other with described forward voltage input; The described second emitter follower circuit comprises second operational amplifier and metal-oxide-semiconductor, and the in-phase input end of described second operational amplifier links to each other with described negative voltage input; The inverting input of described two operational amplifiers all links to each other with described source degeneracy circuit with the source electrode of described metal-oxide-semiconductor; The output of described two operational amplifiers links to each other with the grid of described metal-oxide-semiconductor; The drain electrode of described metal-oxide-semiconductor links to each other with the load circuit that operational amplifier is corresponding separately respectively.
Preferably, above-mentioned variable gain amplifier also can have following characteristics:
Described metal-oxide-semiconductor comprises N type metal-oxide-semiconductor and P type metal-oxide-semiconductor.
Preferably, above-mentioned variable gain amplifier also can have following characteristics:
The described first emitter follower circuit comprises first operational amplifier and triode, and the in-phase input end of described first operational amplifier links to each other with described forward voltage input; The described second emitter follower circuit comprises second operational amplifier and triode, and the in-phase input end of described second operational amplifier links to each other with described negative voltage input; The inverting input of described two operational amplifiers all links to each other with described source degeneracy circuit with the emitter of described triode; The output of described two operational amplifiers links to each other with the base stage of described triode; The collector electrode of described triode links to each other with the load circuit that operational amplifier is corresponding separately.
Preferably, above-mentioned variable gain amplifier also can have following characteristics:
Described first load circuit and described second load circuit comprise load resistance.
Preferably, above-mentioned variable gain amplifier also can have following characteristics:
Described load resistance is an adjustable resistance.
Preferably, above-mentioned variable gain amplifier also can have following characteristics:
Described source degeneracy circuit comprises source degeneracy resistance.
Preferably, above-mentioned variable gain amplifier also can have following characteristics:
Described source degeneracy resistance is adjustable resistance.
Preferably, above-mentioned variable gain amplifier also can have following characteristics:
Described VGA is arranged in radio-frequency (RF) transceiver.
This variable gain amplifier adopts amplifier to constitute emitter follower circuit, and it is simple to have a circuit structure, and circuit area is little, the advantage that the circuit linearity is high.
Description of drawings
Fig. 1 is existing digital Auto Gain control loop schematic diagram;
Fig. 2 is the circuit diagram of the variable gain amplifier of existing control input stage bias current;
Fig. 3 is the circuit diagram of the variable gain amplifier of existing control input stage source degeneracy resistance R E;
Fig. 4 is the circuit diagram of the present invention based on the variable gain amplifier of programmable load.
Embodiment
Below in conjunction with accompanying drawing technical scheme is described in further detail.
The invention provides a kind of variable gain amplifier (VGA), described VGA comprises difference channel, described difference channel comprises first load circuit, second load circuit and source degeneracy circuit, described difference channel also comprises the first emitter follower circuit and the second emitter follower circuit, wherein, the gate/base of the described first emitter follower circuit links to each other with the forward voltage input of described difference channel, and drain/collector links to each other with described first load circuit; The gate/base of the described second emitter follower circuit links to each other with the negative voltage input of described difference channel, and drain/collector links to each other with described second load circuit; The source/emitter of described two emitter follower circuit is connected respectively to the two ends of described source degeneracy circuit.
Wherein, above-mentioned emitter follower circuit can have multiple implementation, for example, the above-mentioned first emitter follower circuit comprises first operational amplifier and metal-oxide semiconductor (MOS) (MOS) pipe, and the in-phase input end of above-mentioned first operational amplifier links to each other with above-mentioned forward voltage input; The above-mentioned second emitter follower circuit comprises second operational amplifier and metal-oxide-semiconductor, and the in-phase input end of above-mentioned second operational amplifier links to each other with above-mentioned negative voltage input; The inverting input of above-mentioned two operational amplifiers all links to each other with above-mentioned source degeneracy circuit with the source electrode of above-mentioned metal-oxide-semiconductor; The output of above-mentioned two operational amplifiers links to each other with the grid of above-mentioned metal-oxide-semiconductor; The drain electrode of above-mentioned metal-oxide-semiconductor links to each other with the load circuit that operational amplifier is corresponding separately respectively.Can also be provided with other elements or the like between the grid of the output of above-mentioned operational amplifier and above-mentioned NMOS pipe; Certain above-mentioned operational amplifier also can be replaced by other elements.
Wherein, above-mentioned metal-oxide-semiconductor comprises N type metal-oxide-semiconductor and P type metal-oxide-semiconductor.
Need to prove that when above-mentioned emitter follower circuit comprised metal-oxide-semiconductor, the drain electrode of the drain electrode of this emitter follower circuit and NMOS pipe (can referring to Fig. 4) was the same utmost point; The source electrode of the source electrode of this emitter follower circuit and NMOS pipe is the same utmost point.
In addition, above-mentioned metal-oxide-semiconductor can also be replaced by triode, and for example above-mentioned first emitter follower circuit comprises first operational amplifier and triode, and the in-phase input end of above-mentioned first operational amplifier links to each other with above-mentioned forward voltage input; The above-mentioned second emitter follower circuit comprises second operational amplifier and triode, and the in-phase input end of above-mentioned second operational amplifier links to each other with above-mentioned negative voltage input; The inverting input of above-mentioned two operational amplifiers all links to each other with above-mentioned source degeneracy circuit with the emitter of above-mentioned triode; The output of above-mentioned two operational amplifiers links to each other with the base stage of above-mentioned triode; The collector electrode of above-mentioned triode links to each other with the load circuit that operational amplifier is corresponding separately.At this moment, the very same utmost point of the current collection of the collector electrode of above-mentioned emitter follower circuit and triode; The very same utmost point of the emitter of above-mentioned emitter follower circuit and the emission of triode.This shows metal-oxide-semiconductor that three utmost points and its of emitter follower circuit comprises or triode three extremely corresponding.
Above-mentioned first load circuit and second load circuit can comprise resistance, and preferably, above-mentioned resistance is adjustable resistance; Resistance in the degeneracy circuit of above-mentioned source is except can also can be fixed resistance, or several resistance string being connected in parallel for the adjustable resistance.
As shown in Figure 4, be the circuit diagram of the present invention based on the variable gain amplifier of programmable load, this VGA comprises two current source I1, I2; Two N type metal oxide semiconductors (NMOS) pipe M1, M2; 3 resistance R 1, R2 and R3; Two operational amplifiers (abbreviation amplifier) OP1, OP2.The The Nomenclature Composition and Structure of Complexes of NMOS pipe M1, M2 is identical with the The Nomenclature Composition and Structure of Complexes of existing programmable trans-conductance device.The two ends of resistance R 2, R3 are connected with power supply (VDD) with the drain electrode of NMOS pipe (M1 and M2) respectively, and the source electrode of (M1 and M2) is managed at the two ends of resistance R 1 respectively with NMOS.The input utmost point of current source (I1, I2) is connected with the source electrode of NMOS pipe respectively, and the output stage of current source (I1, I2) is connected with ground (GND).
Different with existing structure is to have increased operational amplifier, the output of operational amplifier (OP1, OP2) is connected with the grid of NMOS pipe (M1, M2) respectively, the inverting input of operational amplifier (OP1, OP2) is connected with the source electrode of NMOS pipe (M1, M2) respectively, the in-phase input end of operational amplifier (OP1, OP2) is connected with input voltage (Vin+, Vin-) respectively, constitutes the emitter follower circuit.
By selecting the suitable dimension of the inner metal-oxide-semiconductor of operational amplifier, and the size of adjusting NMOS pipe M1, M2, can be so that the voltage of node C1, C2 equal Vin+ and Vin-respectively, and follow Vin+ and Vin-changes and changes.The electric current Δ I that flows through resistance R 3 so just equals:
Simultaneously, because the electric current of current source of flowing through is respectively I1 and I2, branch road A then, the electric current of B is respectively:
Hence one can see that, and output voltage V out+ and Vout-are respectively:
By following formula 11), 12) as can be known, output voltage is with the input voltage linear change, irrelevant with the mutual conductance gm of metal-oxide-semiconductor, this circuit has the good linearity.
In addition, when changing load resistance R2, R3 big or small, output voltage changes thereupon, thereby reaches the purpose that changes gain.
Adopt the variable gain amplifier of emitter follower circuit, it is simple to have a circuit structure, and circuit area is little, the advantage that the linearity is high.
In addition, above-mentioned VGA can also be arranged in radio-frequency (RF) transceiver, owing to this VGA linearity height, goes for the transmitting chain of radio-frequency (RF) transceiver.
Above embodiment is only unrestricted in order to technical scheme of the present invention to be described, only with reference to preferred embodiment the present invention is had been described in detail.Those of ordinary skill in the art should be appreciated that and can make amendment or be equal to replacement technical scheme of the present invention, and do not break away from the spirit and scope of technical solution of the present invention, all should be encompassed in the middle of the claim scope of the present invention.
Claims (9)
1. a variable gain amplifier (VGA), described VGA comprises difference channel, described difference channel comprises first load circuit, second load circuit and source degeneracy circuit, it is characterized in that, described difference channel also comprises the first emitter follower circuit and the second emitter follower circuit, wherein, the grid of the described first emitter follower circuit or base stage link to each other with the forward voltage input of described difference channel, and drain electrode or collector electrode link to each other with described first load circuit; The grid of the described second emitter follower circuit or base stage link to each other with the negative voltage input of described difference channel, and drain electrode or collector electrode link to each other with described second load circuit; The source electrode of described two emitter follower circuit or emitter are connected respectively to the two ends of described source degeneracy circuit.
2. variable gain amplifier according to claim 1 is characterized in that:
The described first emitter follower circuit comprises first operational amplifier and metal-oxide semiconductor (MOS) (MOS) pipe, and the in-phase input end of described first operational amplifier links to each other with described forward voltage input; The described second emitter follower circuit comprises second operational amplifier and metal-oxide-semiconductor, and the in-phase input end of described second operational amplifier links to each other with described negative voltage input; The inverting input of described two operational amplifiers all links to each other with described source degeneracy circuit with the source electrode of described metal-oxide-semiconductor; The output of described two operational amplifiers links to each other with the grid of described metal-oxide-semiconductor; The drain electrode of described metal-oxide-semiconductor links to each other with the load circuit that operational amplifier is corresponding separately respectively.
3. variable gain amplifier according to claim 2 is characterized in that:
Described metal-oxide-semiconductor comprises N type metal-oxide-semiconductor and P type metal-oxide-semiconductor.
4. according to the described variable gain amplifier of claim 1 claim, it is characterized in that:
The described first emitter follower circuit comprises first operational amplifier and triode, and the in-phase input end of described first operational amplifier links to each other with described forward voltage input; The described second emitter follower circuit comprises second operational amplifier and triode, and the in-phase input end of described second operational amplifier links to each other with described negative voltage input; The inverting input of described two operational amplifiers all links to each other with described source degeneracy circuit with the emitter of described triode; The output of described two operational amplifiers links to each other with the base stage of described triode; The collector electrode of described triode links to each other with the load circuit that operational amplifier is corresponding separately.
5. according to claim 2 or the described variable gain amplifier of 4 claims, it is characterized in that:
Described first load circuit and described second load circuit comprise load resistance.
6. variable gain amplifier according to claim 5 is characterized in that:
Described load resistance is an adjustable resistance.
7. variable gain amplifier according to claim 2 is characterized in that:
Described source degeneracy circuit comprises source degeneracy resistance.
8. variable gain amplifier according to claim 7 is characterized in that:
Described source degeneracy resistance is adjustable resistance.
9. variable gain amplifier according to claim 6 is characterized in that:
Described VGA is arranged in radio-frequency (RF) transceiver.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011100534768A CN102104367A (en) | 2011-03-04 | 2011-03-04 | Variable gain amplifier (VGA) |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011100534768A CN102104367A (en) | 2011-03-04 | 2011-03-04 | Variable gain amplifier (VGA) |
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| CN2011100534768A Pending CN102104367A (en) | 2011-03-04 | 2011-03-04 | Variable gain amplifier (VGA) |
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Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102916667A (en) * | 2011-08-02 | 2013-02-06 | 中国科学院微电子研究所 | Broadband programmable gain amplifier with 2dB step length |
| CN102916666A (en) * | 2011-08-02 | 2013-02-06 | 中国科学院微电子研究所 | Broadband programmable gain amplifier |
| CN103051298A (en) * | 2011-10-17 | 2013-04-17 | 中国科学院微电子研究所 | Programmable Gain Amplifier Circuit and Programmable Gain Amplifier |
| CN106936395A (en) * | 2017-03-01 | 2017-07-07 | 中国电子科技集团公司第二十四研究所 | Linear voltage-controlled amplifier |
| CN107800394A (en) * | 2017-12-08 | 2018-03-13 | 成都前锋电子仪器有限责任公司 | A kind of variable gain control circuit |
| CN108023556A (en) * | 2013-03-11 | 2018-05-11 | 华为技术有限公司 | Improved radio frequency low-noise amplifier load circuit |
| CN109672424A (en) * | 2019-02-17 | 2019-04-23 | 平湖市奥特模星电子有限公司 | A kind of reflection-type phase shifter |
| CN113507270A (en) * | 2021-06-23 | 2021-10-15 | 深圳市傲科光电子有限公司 | Variable gain amplifier |
| CN114726321A (en) * | 2022-03-31 | 2022-07-08 | 上海韬润半导体有限公司 | Open-loop operational amplifier circuit |
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| US4163950A (en) * | 1978-03-01 | 1979-08-07 | Tektronix, Inc. | Isolating differential amplifier |
| US4667166A (en) * | 1985-01-28 | 1987-05-19 | Iwatsu Electric Co., Ltd. | Differential amplifier system |
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Cited By (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102916666A (en) * | 2011-08-02 | 2013-02-06 | 中国科学院微电子研究所 | Broadband programmable gain amplifier |
| CN102916666B (en) * | 2011-08-02 | 2015-09-09 | 中国科学院微电子研究所 | Broadband programmable gain amplifier |
| CN102916667B (en) * | 2011-08-02 | 2015-09-09 | 中国科学院微电子研究所 | Broadband programmable gain amplifier with 2dB step length |
| CN102916667A (en) * | 2011-08-02 | 2013-02-06 | 中国科学院微电子研究所 | Broadband programmable gain amplifier with 2dB step length |
| CN103051298A (en) * | 2011-10-17 | 2013-04-17 | 中国科学院微电子研究所 | Programmable Gain Amplifier Circuit and Programmable Gain Amplifier |
| CN103051298B (en) * | 2011-10-17 | 2016-07-06 | 中国科学院微电子研究所 | Programmable Gain Amplifier Circuit and programmable gain amplifier |
| CN108023556A (en) * | 2013-03-11 | 2018-05-11 | 华为技术有限公司 | Improved radio frequency low-noise amplifier load circuit |
| CN106936395A (en) * | 2017-03-01 | 2017-07-07 | 中国电子科技集团公司第二十四研究所 | Linear voltage-controlled amplifier |
| CN106936395B (en) * | 2017-03-01 | 2020-02-07 | 中国电子科技集团公司第二十四研究所 | Linear voltage controlled amplifier |
| CN107800394A (en) * | 2017-12-08 | 2018-03-13 | 成都前锋电子仪器有限责任公司 | A kind of variable gain control circuit |
| CN109672424A (en) * | 2019-02-17 | 2019-04-23 | 平湖市奥特模星电子有限公司 | A kind of reflection-type phase shifter |
| CN113507270A (en) * | 2021-06-23 | 2021-10-15 | 深圳市傲科光电子有限公司 | Variable gain amplifier |
| CN113507270B (en) * | 2021-06-23 | 2024-04-19 | 深圳市傲科光电子有限公司 | Variable gain amplifier |
| CN114726321A (en) * | 2022-03-31 | 2022-07-08 | 上海韬润半导体有限公司 | Open-loop operational amplifier circuit |
| CN114726321B (en) * | 2022-03-31 | 2023-01-31 | 上海韬润半导体有限公司 | Open-loop operational amplifier circuit |
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Application publication date: 20110622 |