CN112910436A - Second-order low-pass active filter integrated circuit for realizing demodulation sampling - Google Patents
Second-order low-pass active filter integrated circuit for realizing demodulation sampling Download PDFInfo
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Abstract
The invention relates to a second-order low-pass active filter integrated circuit for realizing demodulation sampling, which comprises a same-phase amplifier module, a first-order low-pass filter module and a second-order low-pass filter module, wherein the same-phase amplifier module is used for amplifying signals, and the output end of the same-order low-pass filter module realizes the first-order low-pass filter; the passive first-order low-pass filter module comprises a third resistor and an external capacitor, wherein the third resistor is connected with the output end of the in-phase amplifier module, and the external capacitor is connected with the third resistor and used for generating an output end pole for realizing zero offset of the in-phase amplifier module and realizing second-order low-pass filtering characteristics; and the input end of the analog-to-digital converter is connected with the junction of the third resistor and the external capacitor and is used for sampling signals and performing analog-to-digital conversion. The second-order low-pass active filter integrated circuit for realizing demodulation sampling reduces the cost of a PCB, has good single-pole characteristics, can ensure low quality factor of a same-phase amplifier, and can sample accurate information in real time.
Description
Technical Field
The invention relates to the field of communication, in particular to the field of wireless charging, and specifically relates to a second-order low-pass active filter integrated circuit for realizing demodulation sampling.
Background
In the WPC mode wireless charging, information interaction between a sending end and a receiving end is transmitted in a modulation mode of FSK and ASK. The information transmission of the receiving end is mainly realized by changing the natural frequency of an output load or a coil capacitor, meanwhile, a modulation signal appears on a voltage and current carrier (power transmission) of a coil of the transmitting end through coil mutual inductance, and then the modulation signal (information) is demodulated by filtering and amplifying through a low-pass filter of the transmitting end.
The frequency of a modulation signal sent by a receiving end is 2kHz, the frequency of wireless charging power transmission is 100k-300kHz, and the modulation signal is weaker than power transmission, so that the current of a coil needs to be sampled by a current detection resistor at a sending end, the carrier wave attenuation and the modulation signal are amplified by a low-pass amplification filter to demodulate useful information, and finally, the information sampling conversion is carried out by an analog-digital converter in an SAR mode to complete information processing.
Most current schemes for information demodulation are low pass filtering followed by amplification of the samples. For example, a company has a design scheme that first-order low-pass filtering is performed through an external RC, a modulation signal is amplified by 50 times through an in-phase amplifier composed of an active amplifier inside a chip, and finally a digital signal is output through sampling conversion by an analog-to-digital converter, as shown in fig. 1. Icoil represents the current in the coil of the wireless charging transmitting terminal, and comprises power transmission current (carrier wave) and information current (modulation) fed back by the receiving terminal; rs represents a sampling resistor, and Icoil is converted into voltage; r0And C0Forming a passive first-order low-pass filter to filter out unnecessary high-frequency components; OP is an active amplifier, R1、R2And an active amplifier, having low-pass filtering characteristics, R2And R1The ratio of (a) to (b) is the magnification factor. RSVoltage produced via R0And C0After first-order low-pass filtering, the filtered signal is processed by R1、R2And the active amplifier amplifies and filters in a first-order low-pass mode, and the output signal is sampled by an analog-to-digital converter and is subjected to analog-to-digital conversion. Vref reference voltage, 12bits _ out represents a 12bit digital output.
In the signal demodulation scheme in the prior art, the input end adopts an external RC to realize first-order low-pass filtering, so that the design and manufacturing cost of the PCB is increased; the design structure and parameters of an active amplifier in a chip can influence the amplitude-frequency characteristic of a non-inverting amplifier, the first-order low-pass characteristic can be realized under the better condition, the higher quality factor Q can be brought under the worse condition, and the peak appears at the turning frequency, so that signals of other frequencies can be amplified in a super-normal way; under the condition that the output end of the non-inverting amplifier is not provided with an external capacitor, a bandwidth (GBW) which is high enough needs to be designed to improve the response speed of the output end so as to deal with sampling under a high-frequency clock of an analog-to-digital converter, particularly in the example, the analog-to-digital converter in the SAR mode, the resolution of 12bits, the sampling capacitor of 5-10 pF and the clock frequency of 10MHz have extremely high requirements on the GBW of the active amplifier without the output capacitor, otherwise, the sampling information is inaccurate.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a second-order low-pass active filter integrated circuit which has the advantages of small error, accurate signal and wide application range and is used for realizing demodulation and sampling.
In order to achieve the above object, the second-order low-pass active filter integrated circuit of the present invention for realizing demodulation sampling comprises:
the second-order low-pass active filter integrated circuit for realizing demodulation sampling is mainly characterized by comprising the following components:
the in-phase amplifier module is used for amplifying signals, and the output end of the in-phase amplifier module realizes first-order low-pass filtering characteristics;
the passive first-order low-pass filter module comprises a third resistor and an external capacitor, wherein the third resistor is connected with the output end of the in-phase amplifier module, and the external capacitor is connected with the third resistor and used for generating an output end pole for realizing zero offset of the in-phase amplifier module and realizing second-order low-pass filtering characteristics;
and the input end of the analog-to-digital converter is connected with the junction of the third resistor and the external capacitor and is used for sampling signals and performing analog-to-digital conversion.
Preferably, the circuit further comprises a passive first-order low-pass filter module and a sampling resistor, and is used for performing first-order low-pass filtering and generating a signal to the in-phase amplifier module to realize the third-order low-pass filtering amplification characteristic.
Preferably, the non-inverting amplifier module is composed of an active amplifier, a first resistor and a second resistor.
Preferably, the non-inverting amplifier module, the third resistor and the analog-to-digital converter are all integrated inside a chip.
Preferably, the active amplifier is a multi-stage amplifier.
Preferably, the turning frequency of the non-inverting amplifier module satisfies the following formula:
wherein f is1Is the turning frequency, R, of the in-phase amplifier module1Is the resistance value of the first resistor, R2GBW is the resistance of the second resistor, and g is the unity gain-bandwidth product of the active amplifiermp1Transconductance parameter of input terminal inside active amplifier, CCTo compensate for the capacitance of the capacitor.
Preferably, the resistance value of the third resistor and the capacitance value of the external capacitor satisfy the following formula:
wherein, CoutIs the capacitance value of an external capacitor, R3Is the resistance value of the third resistor, f2Is the transition frequency of the third resistor and the external capacitor, CadcSampling capacitance, Δ V, for the analog-to-digital converter inputadcFor the voltage variation after sampling by the A/D converter, Δ VoutIs the accuracy of the sampled voltage.
Preferably, the transconductance g of the output end of the active amplifier of the non-inverting amplifier modulemoSatisfy the requirement ofThe following equation:
wherein R is3Is the resistance of the third resistor.
The second-order low-pass active filter integrated circuit for realizing demodulation sampling of the invention is adopted, and a third resistor R is newly added3And an external capacitor CoutThe circuit has the characteristic of first-order low-pass filtering, an RC circuit at the input end of the original circuit can be omitted, and the cost of the PCB is reduced. The newly added third resistor R in the invention3And an external capacitor CoutThe AC loop of the active amplifier has good single-pole characteristics, and can ensure low quality factor of the in-phase amplifier and no peak at the turning frequency. Because of the single-pole characteristic of the active amplifier, the invention can easily design the self turning frequency of the in-phase amplifier by adjusting the unit gain bandwidth product GBW of the active amplifier; the input end of the analog-digital converter is connected to the position of the external capacitor, so that the analog-digital converter has good help for high-frequency sampling of the analog-digital converter, can sample accurate information in real time, and reduces the GBW design requirement on an active amplifier. The invention can easily realize the circuit requirement of the third-order low-pass filter under the condition of keeping the RC circuit at the input end of the original circuit.
Drawings
Fig. 1 is a schematic diagram of a low-pass filtering, amplifying and sampling circuit in the prior art.
Fig. 2 is a schematic diagram of a second-order low-pass filtering, amplifying and sampling circuit of the second-order low-pass active filter integrated circuit for realizing demodulation and sampling according to the invention.
Fig. 3 is a schematic diagram of a third-order low-pass filtering, amplifying and sampling circuit according to an embodiment of the invention.
Fig. 4 is a simplified internal circuit diagram of the rail-to-rail output of the active amplifier of the second order low pass active filter integrated circuit implementing demodulation sampling according to the present invention.
Fig. 5 is a schematic circuit diagram of the output terminal of the non-inverting amplifier of the second-order low-pass active filter integrated circuit for implementing demodulation sampling according to the present invention, which is connected in series with a third resistor and an external capacitor.
Fig. 6 is a schematic diagram of a small signal model for performing loop analysis on the output terminal of the non-inverting amplifier according to the present invention.
FIG. 7 is a schematic diagram of the amplitude-frequency characteristic of the output terminal of the non-inverting amplifier under the condition of high Q value of the circuit of the present invention.
FIG. 8 is a schematic diagram of the amplitude-frequency characteristic of the output terminal of the non-inverting amplifier under the condition of low Q value of the circuit of the present invention.
Detailed Description
In order to more clearly describe the technical contents of the present invention, the following further description is given in conjunction with specific embodiments.
The invention relates to a second-order low-pass active filter integrated circuit for realizing demodulation sampling, which comprises:
the in-phase amplifier module is used for amplifying signals, and the output end of the in-phase amplifier module realizes first-order low-pass filtering characteristics;
the passive first-order low-pass filter module comprises a third resistor and an external capacitor, wherein the third resistor is connected with the output end of the in-phase amplifier module, and the external capacitor is connected with the third resistor and used for generating an output end pole for realizing zero offset of the in-phase amplifier module and realizing second-order low-pass filtering characteristics;
and the input end of the analog-to-digital converter is connected with the junction of the third resistor and the external capacitor and is used for sampling signals and performing analog-to-digital conversion.
As a preferred embodiment of the present invention, the circuit further includes a passive first-order low-pass filter module and a sampling resistor, and is configured to perform first-order low-pass filtering and generate a signal to the non-inverting amplifier module, so as to implement a third-order low-pass filtering amplification characteristic.
In a preferred embodiment of the present invention, the non-inverting amplifier module comprises an active amplifier, a first resistor and a second resistor.
As a preferred embodiment of the present invention, the non-inverting amplifier module, the third resistor and the analog-to-digital converter are all integrated inside a chip.
In a preferred embodiment of the present invention, the active amplifier is a multi-stage amplifier.
As a preferred embodiment of the present invention, the turning frequency of the in-phase amplifier module satisfies the following formula:
wherein f is1Is the turning frequency, R, of the in-phase amplifier module1Is the resistance value of the first resistor, R2GBW is the resistance of the second resistor, and g is the unity gain-bandwidth product of the active amplifiermp1Transconductance parameter of input terminal inside active amplifier, CCTo compensate for the capacitance of the capacitor.
As a preferred embodiment of the present invention, the resistance value of the third resistor and the capacitance value of the external capacitor satisfy the following formula:
wherein, CoutIs the capacitance value of an external capacitor, R3Is the resistance value of the third resistor, f2Is the transition frequency of the third resistor and the external capacitor, CadcSampling capacitance, Δ V, for the analog-to-digital converter inputadcFor the voltage variation after sampling by the A/D converter, Δ VoutIs the accuracy of the sampled voltage.
As a preferred embodiment of the present invention, the transconductance g of the output end of the active amplifier of the non-inverting amplifier modulemoThe following formula is satisfied:
wherein R is3Is the resistance of the third resistor.
In the specific implementation mode of the invention, a third resistor is integrated at the output end of the active amplifier, then a capacitor is externally connected, and the input end of the analog-to-digital converter is connected to the junction point of the resistor and the capacitor. The first-order filtering turning frequency of the non-inverting amplifier of the invention can be adjusted by adjusting the transconductance g of the input end of the active amplifiermp1And a compensation capacitor CcAre calculated. According to the change of the output end turning frequency and the charge of the sampling capacitor of the analog-to-digital converter being equal to CoutCalculating the external capacitance C according to the change of the chargeoutAnd a third resistor R3. According to the calculated third resistance R3Adjusting the width-to-length ratio (W/L) of output tube of active amplifier to 1/gmoLess than R3The active amplifier is made to present a single pole characteristic. As shown in fig. 1 to 3, a dotted frame part indicates an internal circuit of the chip.
(1) Second-order low-pass active filter integrated circuit:
as shown in fig. 2, a resistor is connected in series with the output end of the non-inverting amplifier, and then a capacitor with nF level is externally connected, so that the input end of the analog-to-digital converter is connected to the junction of the resistor and the capacitor, and the RC of the input end of the original circuit is omitted. The carrier is amplified by the in-phase amplifier and then filtered by the output capacitor. Because of the gain frequency characteristic of the active amplifier, the in-phase amplifier also has the low-pass filtering characteristic, so that the carrier wave is attenuated after passing through the in-phase amplifier, and the normal operation of the active amplifier is not influenced. As can be seen from FIG. 2, the third resistor R3Within the dashed box, i.e. representing the third resistance R3The invention is integrated in the chip, improves the circuit structure and reduces the cost of the PCB.
R in FIG. 23And CoutForm a passive first-order low-pass filter while R3And CoutProducing a zero-point to cancel R1、R2Same as active amplifierThe output end pole of the phase amplifier module is made to be a single-pole in-phase amplifier. CoutThe voltage sampling method is beneficial to the real-time and accurate voltage sampling of the analog-to-digital converter. RSThe generated voltage is passed through R1、R2Amplifying in phase with an active amplifier and filtering in low pass in first order, and then passing through R3And CoutFirst-order low-pass filtering is carried out, and finally C is carried outoutGenerates the required low voltage and is sampled and read by the analog-to-digital converter to generate 12-bit digital information.
(2) The embodiment of the third-order low-pass filtering amplification sampling circuit is realized as follows:
as shown in fig. 3, an embodiment of the third-order low-pass filtering, amplifying and sampling circuit implemented by the present invention is as follows:
the circuit of fig. 3 adds the prior art R as shown in fig. 10And C0An electrical circuit. RSThe generated voltage is passed through R0And C0The circuit is first-order low-pass filtered to generate a signal1、R2Amplifying in phase with active amplifier, filtering in low-pass mode, and R3And CoutFirst-order low-pass filtering is carried out, and finally required low voltage is generated on Cout and is sampled and read by an analog-to-digital converter, and 12-bit digital information is generated.
(3) The parameter calculation process of the second-order low-pass active filter integrated circuit comprises the following steps:
and analyzing and researching the amplitude-frequency characteristic of the output end of the in-phase amplifier. The transfer function of the non-inverting amplifier output to input is as follows:
where H(s) represents the transfer function of the in-phase amplifier, f (A) is the transfer function of the active amplifier, and β is the feedback factor (R)1/R2)。
Assuming that the active amplifier is a single-pole system, then
Where A is the DC gain of the active amplifier, p1Is the dominant pole of the active amplifier, then has
Wherein GBW ═ p1A/2 pi is the unity gain bandwidth product of the active amplifier.
From the above equation, the dc gain of the non-inverting amplifier is 1/β, the inflection frequency is GBW β, and the amplitude-frequency curve smoothly transits at the inflection frequency without a peak, as shown in fig. 8. This is the characteristic that the low-pass filter of the present invention is to satisfy.
If the active amplifier is a two-pole system, then
Where A is the DC gain of the active amplifier, p1Is the dominant pole, p, of the active amplifier2Is the secondary pole, p1And p2Representing the circular frequency, then:
it can be seen that h(s) is a bi-polar function, belonging to a second order system, with dc gain still equal to 1/β. The amplitude-frequency characteristic of h(s) can be determined by solving the root of the denominator of the above equation. The transition frequency ω can also be calculated by the transfer function of a standard second order low pass filter (see below)0And a quality factor Q, and a quality factor,
at the transition frequency omega0The amplitude of H(s) is shown by the formula:
as can be seen from the above formula, the values of p1, p2, A and beta are different, the Q value can be larger than 1, and H(s) is at omega0There occurs an increase in amplification (spike) phenomenon, as shown in fig. 7, which is a characteristic to be avoided by the low pass filter of the present invention. In order to avoid the peak hidden trouble, the active amplifier needs to be a single-pole system, and the peak is eliminated fundamentally.
Considering that the active amplifier is used for amplification of the modulated signal, wide swing of the output, to the capacitor CoutThe output of the driver needs to adopt a rail-to-rail structure of class AB, and at the same time, the gain of the input signal needs to be high enough, so that the active amplifier is at least a two-stage amplifier, as shown in fig. 4. The two-stage amplifier has two high-resistance nodes, and two poles are formed by the two-stage amplifier and corresponding capacitors, so that the two-stage amplifier belongs to a two-pole system. One of them is the low frequency dominant pole, which is generated by the output resistance of the first stage amplifier and the compensating miller capacitance (position a +/a-in fig. 4); the second high-frequency secondary pole is positioned at the output end, and according to the prior theoretical experience, the secondary pole is as follows
Wherein, gmoRepresents the sum of the transconductances, C, of output tubes MP0 and MN0outRepresenting the output external capacitance or parasitic capacitance.
As shown in fig. 5, if the resistor R is connected in series at the output terminal3And a capacitor CoutThen, according to the small signal model set up in FIG. 6, loop analysis and calculation are performed, the position of the main pole point is unchanged, and the output end of the function is partially changed, such asThe following:
wherein A represents a DC gain, fL(A) The low frequency related part of the function is represented and does not affect the high frequency analysis, which is ignored here.
From the above formula, if only the capacitor (i.e. R) is connected in series at the output terminal30), the output end only generates a pole, the active amplifier presents a double-pole system, and the non-inverting amplifier has the hidden trouble of amplitude-frequency spike. If the output end of the active amplifier is connected with the resistor R in series3The output terminal will generate zero point again. If R is3Can approach or even be more than 1/gmoAnd the zero poles at the output end are mutually offset, the active amplifier has a single-pole characteristic, and the in-phase amplifier fundamentally eliminates the hidden trouble of amplitude-frequency peaks. Therefore, the output end of the active amplifier is connected with the resistor R in series3And a capacitor CoutThe active amplifier may be designed for a single pole characteristic. On the other hand, the series-connected resistors R3And a capacitor CoutItself also being a passive low pass filter, R3And CoutThe node of (a) is the low-pass filtered output.
In summary, as shown in fig. 2, the active amplifier of the improved low-pass filtering amplifier circuit exhibits a single-pole characteristic, and the non-inverting amplifier of the improved low-pass filtering amplifier circuit exhibits a first-order low-pass filtering characteristic at the output terminal of the active amplifier, and then combines with R3CoutThe first-order low-pass characteristic of the capacitor C shows a second-order low-pass filtering characteristic at the input end of the analog-to-digital converter and amplifies the modulation signaloutAnd the voltage sampling of the analog-to-digital converter is real-time and accurate. If the R of the original circuit is reserved at the input end of the non-inverting amplifier, as shown in FIG. 30C0Thus, the third-order low-pass filtering amplification characteristic can be presented. In the above structure design, the low-pass filters of each stage are connected in series, so that the input end of the analog-to-digital converter is connected to the current-detecting resistor RSThe transfer function of the terminal can be expressed as follows:
in the above formula, the left bracket term represents the input end R of the non-inverting amplifier0C0Composed of a first-order passive filter, an active amplifier represented by the middle bracket term, and an R1/R2Formed first order active filter and amplifying R2/R1The rightmost bracket term represents the output end R of the in-phase amplifier3CoutAnd forming a first-order passive filter. Therefore, the parameters of each stage of filter can be flexibly and conveniently designed.
Determining the turning frequency of the low-pass filtering according to the requirement of the system on signal filtering, and calculating some parameters on the circuit design by inverse deduction of the turning frequency, wherein the calculation process of the circuit parameters is as follows:
1. design on some parameters of the in-phase amplifier. From the above formula, the turning frequency of the non-inverting amplifier is GBWR1/R2GBW is the unity gain bandwidth product of the active amplifier. For an active amplifier with miller compensation capacitance, GBW ═ gmp1/(2π*2Cc)，gmp1And can pass through ItailAnd the channel width to length ratios of mp1 and mp 2. The transconductance g of the input in fig. 4 is thus calculated from the reverse extrapolation of the corner frequencymp1And a compensation capacitor Cc。CcUsually a few pF, gmp1Parameters of the input end pipe can be determined. R1/R2Determined by the amplification of the in-phase amplifier.
2. R connected in series with output end of active amplifier3CoutThe design of the parameters of (1). According to the turning frequency 1/(2 pi C)outR3) One of the parameters is determined, and the other parameter is calculated. According to the size and initial value of the sampling capacitor of the analog-to-digital converter and the requirement on the sampling voltage precision, the change of the charge of the sampling capacitor of the analog-to-digital converter is equal to CoutDesigning capacitance C according to the relation of charge changeoutThe larger the capacitance (nF magnitude) is, the more beneficial the accuracy of the analog-to-digital converter for sampling voltage is, but the active amplifier output end is required to have the capacitance CoutThe stronger the driving capability. Suppose the sampling capacitance at the input end of the analog-to-digital converter is CadcVoltage change Δ V after samplingadcPrecision of sampling voltage is DeltaVoutAccording to the relationship of the equal change of the charges of the two capacitors, then
Calculate CoutThen, R is calculated from the transition frequency3。
3. Design of transconductance g of active amplifier outputmo. Designed CoutAnd R3In order for the active amplifier to exhibit a single-pole characteristic, 1/g is requiredmoIs close to or less than R3. As shown in FIG. 4, g can be adjusted by adjusting the width-to-length ratio (W/L) of mp0 and mn0 tubesmo. The larger the width-to-length ratio, 1/gmoSmaller and simultaneously beneficial to driving the output capacitor C with large swingout. Thus consisting of gmoAnd designing parameters of the output end pipe.
4. In the embodiment shown in FIG. 3, the filter circuit R is based on the input of the non-inverting amplifier0C0Has a turning frequency of 1/(2 pi 2R)0C0) Calculate R0And C0. General requirements C0Values close to μ F, so that R can be adjusted0C0The serial connection relationship between the independent circuit and the subsequent circuit does not affect the analysis of the circuit and the calculation of parameters. From C0After the value is taken, R is determined0。
The invention improves the second-order low-pass active filter integrated circuit applied to the demodulation sampling of the WPC wireless charging transmitting terminal, adds an external capacitor, and the improved circuit can also amplify the modulation signal and realize second-order roll-off attenuation on carrier waves and other high-frequency signals; the improved circuit can control the quality factor Q of the second-order low-pass active filter in a lower range, and avoid unnecessary peaks near the turning frequency; on the basis of improving the circuit, if the RC of the original circuit is kept at the input end of the filter, a third-order low-pass effect can be realized, and 60 dB/ten frequency multiplication attenuation is carried out on a carrier; the external capacitor can be simultaneously beneficial to the accurate and rapid sampling of the signals by the analog-to-digital converter in the SAR mode under the high-frequency clock frequency (such as 10MHz), so that the bandwidth of the filter amplifier is not required to be extremely high to meet the response speed under the high-frequency clock.
The second-order low-pass active filter integrated circuit for realizing demodulation sampling of the invention is adopted, and a third resistor R is newly added3And an external capacitor CoutThe circuit has the characteristic of first-order low-pass filtering, an RC circuit at the input end of the original circuit can be omitted, and the cost of the PCB is reduced. The newly added third resistor R in the invention3And an external capacitor CoutThe AC loop of the active amplifier has good single-pole characteristics, and can ensure low quality factor of the in-phase amplifier and no peak at the turning frequency. Because of the single-pole characteristic of the active amplifier, the invention can easily design the self turning frequency of the in-phase amplifier by adjusting the unit gain bandwidth product GBW of the active amplifier; the input end of the analog-digital converter is connected to the position of the external capacitor, so that the analog-digital converter has good help for high-frequency sampling of the analog-digital converter, can sample accurate information in real time, and reduces the GBW design requirement on an active amplifier. The invention can easily realize the circuit requirement of the third-order low-pass filter under the condition of keeping the RC circuit at the input end of the original circuit.
In this specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.
Claims (8)
1. A second order low pass active filter integrated circuit for implementing demodulated samples, the circuit comprising:
the in-phase amplifier module is used for amplifying signals, and the output end of the in-phase amplifier module realizes first-order low-pass filtering characteristics;
the passive first-order low-pass filter module comprises a third resistor and an external capacitor, wherein the third resistor is connected with the output end of the in-phase amplifier module, and the external capacitor is connected with the third resistor and used for generating an output end pole for realizing zero offset of the in-phase amplifier module and realizing second-order low-pass filtering characteristics;
and the input end of the analog-to-digital converter is connected with the junction of the third resistor and the external capacitor and is used for sampling signals and performing analog-to-digital conversion.
2. The integrated circuit of claim 1, further comprising a passive first-order low-pass filter module and a sampling resistor for performing first-order low-pass filtering and generating a signal to the in-phase amplifier module to realize third-order low-pass filtering and amplifying characteristics.
3. The second-order low-pass active filter integrated circuit for performing demodulation sampling according to claim 1, wherein the in-phase amplifier module comprises an active amplifier, a first resistor and a second resistor.
4. The second-order low-pass active filter integrated circuit for sampling demodulation of claim 1, wherein the non-inverting amplifier module, the third resistor and the analog-to-digital converter are all integrated inside a chip.
5. The second-order low-pass active filter integrated circuit of claim 3, wherein the active amplifier is a multi-stage amplifier.
6. The second-order low-pass active filter integrated circuit for performing demodulation sampling according to claim 1, wherein the turning frequency of the in-phase amplifier module satisfies the following formula:
wherein f is1Is the turning frequency, R, of the in-phase amplifier module1Is the resistance value of the first resistor, R2GBW is the resistance of the second resistor, and g is the unity gain-bandwidth product of the active amplifiermp1Transconductance parameter of input terminal inside active amplifier, CCTo compensate for the capacitance of the capacitor.
7. The second-order low-pass active filter integrated circuit for realizing demodulation sampling according to claim 1, wherein the resistance value of the third resistor and the capacitance value of the external capacitor satisfy the following formula:
wherein, CoutIs the capacitance value of an external capacitor, R3Is the resistance value of the third resistor, f2Is the transition frequency of the third resistor and the external capacitor, CadcSampling capacitance, Δ V, for the analog-to-digital converter inputadcFor the voltage variation after sampling by the A/D converter, Δ VoutIs the accuracy of the sampled voltage.
8. The second-order lowpass active filter integrated circuit of claim 1, wherein transconductance g of the output of the active amplifier of the non-inverting amplifier block is configured to be equal tomoThe following formula is satisfied:
wherein R is3Is the resistance of the third resistor.
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| JPH07283690A (en) * | 1994-04-09 | 1995-10-27 | Kenwood Corp | Differential low-pass filter |
| CN1811487A (en) * | 2006-03-08 | 2006-08-02 | 中南大学 | Preamplification and filtering circuit for precision isolated amplifier |
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| CN107525781A (en) * | 2016-06-22 | 2017-12-29 | 许亚夫 | A kind of infrared spectrometer amplifies sample circuit |
| CN207399155U (en) * | 2017-11-03 | 2018-05-22 | 国网江苏省电力公司电力科学研究院 | Signal filtering process Compare System based on analog-digital converter |
| CN109302192A (en) * | 2018-11-16 | 2019-02-01 | 上海工程技术大学 | A kind of universal demodulation device |
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2019
- 2019-12-03 CN CN201911220940.0A patent/CN112910436A/en active Pending
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| JPH07283690A (en) * | 1994-04-09 | 1995-10-27 | Kenwood Corp | Differential low-pass filter |
| CN1811487A (en) * | 2006-03-08 | 2006-08-02 | 中南大学 | Preamplification and filtering circuit for precision isolated amplifier |
| CN107525781A (en) * | 2016-06-22 | 2017-12-29 | 许亚夫 | A kind of infrared spectrometer amplifies sample circuit |
| CN106101585A (en) * | 2016-07-27 | 2016-11-09 | 中国科学院西安光学精密机械研究所 | A kind of low noise CCD camera circuitry |
| CN207399155U (en) * | 2017-11-03 | 2018-05-22 | 国网江苏省电力公司电力科学研究院 | Signal filtering process Compare System based on analog-digital converter |
| CN109302192A (en) * | 2018-11-16 | 2019-02-01 | 上海工程技术大学 | A kind of universal demodulation device |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114337600A (en) * | 2022-03-11 | 2022-04-12 | 华南理工大学 | On-chip differential active RC filter calibration and tuning method |
| CN114337600B (en) * | 2022-03-11 | 2022-06-03 | 华南理工大学 | On-chip differential active RC filter calibration and tuning method |
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