CN114448362A - Current signal amplifying circuit suitable for multi-scene requirements - Google Patents
Current signal amplifying circuit suitable for multi-scene requirements Download PDFInfo
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- CN114448362A CN114448362A CN202111544399.6A CN202111544399A CN114448362A CN 114448362 A CN114448362 A CN 114448362A CN 202111544399 A CN202111544399 A CN 202111544399A CN 114448362 A CN114448362 A CN 114448362A
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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
- H03F1/26—Modifications of amplifiers to reduce influence of noise generated by amplifying elements
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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
- H03F1/42—Modifications of amplifiers to extend the bandwidth
- H03F1/48—Modifications of amplifiers to extend the bandwidth of aperiodic amplifiers
- H03F1/486—Modifications of amplifiers to extend the bandwidth of aperiodic amplifiers with IC amplifier blocks
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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
- H03F3/68—Combinations of amplifiers, e.g. multi-channel amplifiers for stereophonics
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F2200/00—Indexing scheme relating to amplifiers
- H03F2200/361—Transistor with multiple collectors
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F2200/00—Indexing scheme relating to amplifiers
- H03F2200/372—Noise reduction and elimination in amplifier
Abstract
The invention provides a current signal amplifying circuit suitable for multi-scene requirements, which can realize optimization of different performance parameters of bandwidth and noise in the same amplifying circuit according to application requirements of amplifying low-noise and high-bandwidth different current signals. The invention comprises an optional low noise amplifier, a T-type feedback network, a zero compensation network, an offset adjustment and a low pass filter. The selectable low-noise amplifier is suitable for different application scenes; the T-shaped feedback network improves the gain of the amplifying circuit; the zero compensation network promotes the gain of the amplifying circuit within thousands of Hz to several megaHz and expands the bandwidth of the amplifying circuit; the bias adjustment adjustable circuit bias; the low-pass filter circuit adopts an MFP circuit to realize low-pass filtering. The invention can effectively improve the performances of noise, gain, bandwidth, drift and the like of the current amplifying circuit according to different application scenes, and can realize high gain, high bandwidth and low noise.
Description
Technical Field
The invention relates to the technical field of precision analysis and measurement, in particular to a current signal amplifying circuit suitable for multi-scene requirements.
Background
In medium and high-end analytical instruments such as ion mobility spectrometry, infrared spectroscopy, mass spectrometry and the like, a weak current signal (pA level) needs to be amplified, and the measurement of the weak current signal is the key of the whole detection process. When a weak current signal is measured, the noise and the bandwidth of the amplifier are difficult to be considered simultaneously. In the ultra-low noise current amplification application, the bandwidth requirement of the amplifier is narrow, and in the high bandwidth current amplification application, the noise requirement of the amplifier is low, so that a proper amplifier needs to be selected according to different application scenes. The smaller the weak current signal is, the higher the gain requirement of an amplifying circuit needing to be designed is, the larger the selected feedback resistor is, the higher the precision requirement is, and the conventional resistor is difficult to realize. Meanwhile, when the gain of the circuit is higher, the feedback resistance of the circuit is larger, and the parasitic capacitance of the circuit can significantly influence the bandwidth of the amplifying circuit. At 10-8For example, when the feedback resistor is 100M, the parasitic capacitance of 1pF introduces a pole near 100kHz, which greatly limits the bandwidth of the amplifier circuit. Therefore, for broadband weak current signal amplification, a compensation circuit is required to be added to offset a pole introduced by a circuit parasitic capacitance. For measuring weak current signals, the circuit gain is high, the self bias of the circuit often causes the output bias of the circuit to be overlarge or even saturated, and the dynamic range of the amplifying circuit is limited, so that the high-gain amplifier must be provided with a corresponding zero setting circuit to offset the bias current of the high-gain amplifier, and the dynamic range of the high-gain amplifier is improved. The current amplifying circuit can not meet the application requirements of amplifying low-noise and high-bandwidth different current signals, and can not realize the optimization of different performance parameters of bandwidth and noise in the same amplifying circuit.
Disclosure of Invention
In view of this, the present invention provides a current signal amplifying circuit suitable for multi-scenario requirements, which can achieve optimization of different performance parameters of bandwidth and noise in the same amplifying circuit according to application requirements of amplifying current signals with different bandwidths, i.e., low noise and high bandwidth.
In order to achieve the purpose, the technical scheme of the invention is as follows:
(in accordance with the content of the claims)
Has the advantages that:
the invention discloses a novel method for improving the performance of a high-gain high-bandwidth low-noise current signal amplification circuit, which comprises a selectable low-noise amplifier, a T-shaped feedback network, a zero compensation network, an offset adjustment and a low-pass filter. The selectable low-noise amplifier adopts two ultra-low voltage noise operational amplifiers, and selects a corresponding low-noise amplifier according to the requirements of noise and bandwidth to adapt to different application scenes; the T-type feedback network equivalently converts the resistance of the quantity series megaohm into dozens of times of the original resistance by utilizing the characteristics of the T-type circuit, so that the gain of the amplifying circuit is improved; the zero point compensation network promotes the gain of the amplifying circuit within thousands of Hz to several megaHz and expands the bandwidth of the amplifying circuit by a zero point compensation mode; the bias adjustment adjustable circuit bias; the low-pass filter circuit adopts an MFP circuit to realize low-pass filtering. The invention can effectively improve the performances of noise, gain, bandwidth, drift and the like of the current amplifying circuit according to different application scenes, and can realize high gain, high bandwidth and low noise.
Drawings
Fig. 1 is a block diagram of the circuit structure of the present invention.
Fig. 2 is a schematic circuit diagram of the present invention.
Fig. 3 is a schematic diagram of a high bandwidth amplifying circuit according to the present invention.
FIG. 4 is a schematic diagram of a low noise amplifier circuit according to the present invention.
Fig. 5 is a schematic diagram illustrating layout adjustment of a T-type feedback network according to the present invention.
Fig. 6 is a schematic diagram illustrating layout adjustment of the RC zero compensation network according to the present invention.
Fig. 7 is an amplitude-frequency response curve of an amplifying circuit with an RC zero compensation network.
Fig. 8 is a schematic diagram of a typical application circuit of the present invention given specific circuit parameters.
Detailed Description
The invention is described in detail below by way of example with reference to the accompanying drawings.
The circuit structure block diagram of the invention is shown in fig. 1, and the circuit structure block diagram shows the connection relationship of the selectable low noise amplifier, the T-shaped feedback network, the zero point compensation network, the bias adjustment and the low pass filter. The amplifying circuit comprises an optional low noise amplifier, a T-shaped feedback network, a zero point compensation network, an offset adjustment and a low-pass filter. The selectable low-noise amplifier can be injected with weak current signals, and the output of the low-noise amplifier is respectively connected with the T-shaped feedback network, the zero compensation network and the low-pass filter; the T-shaped feedback network and the zero compensation network form a double feedback network, and the amplified signal is fed back to the reverse input stage of the amplifier; the bias adjustment is connected with the reverse input of the amplifier, and the circuit bias can be adjusted; the low-pass filter is an output stage and outputs the amplified signal. The circuit schematic of the present invention is shown in fig. 2.
The selectable low noise amplifier is composed of' LNA1"(high bandwidth operational amplifier)," LNA2 "(low noise operational amplifier) and four sets of relays. Wherein the LNA1A broadband operational amplifier is selected, the input impedance is more than or equal to 300M omega, the unit gain bandwidth reaches 50MHz, and the LNA2Selecting a low-noise operational amplifier with input impedance of not less than 1013Omega, the input bias current is less than or equal to 1pA, and a proper operational amplifier is selected as a pre-amplifier through a relay. When LNA is selected1When used as a preamplifier, the amplifier circuit has a high bandwidth and the LNA2As a unity gain amplifier, driving a bias voltage; conversely, when the LNA is selected2When used as a preamplifier, the amplifier circuit has low noise and the LNA1As a unity gain amplifier, a bias voltage is driven. Four groups of relays are used as switches, the on-resistance of the relays is extremely low (less than or equal to 1 omega), and corresponding paths can be selected. In particular, the LNA is chosen1(high bandwidth operational amplifier) as a signal amplifier, the circuit is shown in fig. 3. The input impedance of the broadband operational amplifier LT1028 is larger than or equal to 300M omega, the unit gain bandwidth reaches 50MHz, the input bias current is 25nA, and the broadband operational amplifier LT1028 can be applied to amplification of ultra-wideband current signals. At this time, the LNA2As a unity gain amplifier, driving a bias adjustment voltage; selecting LNA2(Low noise operational amplifier) as a signal amplifier, the circuit is shown in FIG. 4. The input impedance of the ultra-low noise operational amplifier AD549 is not less than 1013Omega, transportThe bias current is less than or equal to 1pA, and the method can be applied to amplification of ultralow noise current signals. At this time, the LNA1As a unity gain amplifier, the bias adjustment voltage is driven.
And the T-shaped feedback network and the zero compensation network form a double-channel feedback network. The T-shaped feedback network adopts resistance + resistance (R)T1、RT2、RT3) The structure, three resistance values can be according to the application occasion developments adjustment, utilizes T type circuit characteristics, improves the resistance value equivalence tens to thousands times, improves the feedback resistance value. The schematic diagram of the layout adjustment of the T-shaped feedback network of the invention is shown in FIG. 5, and the working principle of the feedback circuit is derived by combining with FIG. 5, in FIG. 5, the T-shaped resistor is used as the operational amplifier feedback network, RT1、RT2、RT3The value of the feedback resistor is determined according to actual requirements. VinFor the input voltage, VoTo output a voltage, VmIs RT3And node voltage is determined, the operational amplifier virtual short virtual break and kirchhoff current law are adopted, wherein the node voltage relation satisfies the relation:
the equivalent feedback resistance R of the amplifier can be obtained by simplifying the formula (1)T
As can be seen from the formula (2), when R isT3When approaching infinity, the feedback resistance is RT1+RT2(ii) a When R isT1>>RT2，RT2、RT3At the same order of magnitude, equation (2) can be converted into
The transformed equivalent feedback network is brought into the simplified amplifier as shown in fig. 5, RTIs equivalent toA feedback resistance. RT1Is a main feedback resistor, and generally has a larger value, RT2、RT3Usually smaller, by RT2、RT3With proper value, the feedback resistor R can be adjustedT1Let down RT2/RT3And (4) doubling.
Let R beT1The resistance value is 100 MOmega and the resistance RT2Take 1k Ω, RT3Take 100 Ω, i.e.
The selectable low noise amplifier and the T-type feedback network form the amplifier of the whole amplifying circuit when R is higher than RT1>>RT2Then, the gain satisfies:
the zero point compensation network adopts 'resistance + capacitance' (R)f、CfAnd OPA2) A series configuration as shown in fig. 6. The zero compensation network is used as a part of negative feedback of the amplifying circuit, a zero is added in the working frequency range of the circuit, and the frequency point f of the circuit is improvedLThe gain within the range can improve the high-frequency gain of the circuit and enhance the stability of the circuit. A zero point with the turning frequency of thousands of Hz to several megaHz is added to the circuit in a zero point compensation mode, so that the dynamic amplification performance of the circuit in thousands of Hz to several megaHz is improved. The zero frequency of the zero compensation network is:
according to the working frequency range of the circuit, the proper feedback capacitor C is selectedfAdjusting the adjustable resistance RfThe amplitude-frequency response of the amplifying circuit can be optimized. Suppose Cf＝680pF，Rf330 Ω available:
by adjusting the adjustable resistance RfThe magnitude further optimizes its amplitude-frequency response and the unity gain optimization effect is shown in fig. 7.
The bias adjusting circuit is biased, the output of the bias adjusting circuit is connected with the input of the low noise amplifier, and the bias adjusting circuit is provided with an operational amplifier (OPA)1High-precision adjustable resistor RBias1And a resistor RBias2Resistance RBia3And (4) forming. OPA (optical power amplifier) is adjusted by adjusting adjustable resistance1And the input voltage is attenuated by the operational amplifier to provide a weak bias voltage signal for the low-noise amplifier. Usually, the self bias voltage of the low noise amplifier is about uV level, and the adjustable resistor R is under the positive and negative supply voltages VDD and VEEBiasGenerally, several k Ω, and the adjusting resistance is Δ R, then the bias voltage adjusting precision is:
if the adjustable resistor has the adjustment precision of 1% and the resistance value of 1k omega, taking R under the voltage of +/-2.5VBias2＝10kΩ，RBias3When the bias voltage is 10 Ω, the bias voltage is adjusted with the accuracy
By an operational amplifier OPA1High-precision adjustable resistor RBias1And a resistor RBias2And a resistance RBia3And (4) forming.
The low-pass filter is an output stage, the input of the low-pass filter is connected with the output of the low-noise amplifier, and the low-pass filter is composed of an operational amplifier (OPA)3Resistance RLF1、RLF2、RLF3And a capacitor CLF1、CLF2An MFP type low-pass filter circuit is constituted, the cutoff frequency of which is not more than 1 MHz. The cut-off frequency satisfies:
if R is takenLF1＝RLF3＝12k，RLF2＝2k，CLF1＝0.1nF，CLF210pF, its cutoff frequency is:
FIG. 8 shows an example of a typical application, in which specific operational amplifier, resistor, capacitor, etc. model parameters are given, and the gain of the amplifying circuit is up to 1 × 1010V/A, can switch over the leading low-noise amplifier, meet the application of different scenes of ultra-high bandwidth (1MHz) and ultra-low noise (pA level).
In summary, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. A current signal amplifying circuit suitable for multi-scene requirements is characterized by comprising a selectable low-noise amplifier, a T-shaped feedback network, a zero compensation network, an offset adjustment circuit and a low-pass filter;
the selectable low-noise amplifier is connected with the output ends of the T-shaped feedback network and the zero compensation network in a reverse input mode, and the output ends of the selectable low-noise amplifier are respectively connected with the T-shaped feedback network, the zero compensation network and the low-pass filter; the input of the T-shaped feedback network is connected with the output of the low-noise amplifier, and the output of the T-shaped feedback network is fed back to the reverse input of the low-noise amplifier; the input of the zero compensation network is connected with the output of the low noise amplifier, and the output is fed back to the reverse input of the low noise amplifier; the bias adjusting output is connected with the negative input of the low-noise amplifier, and the weak bias voltage of the circuit is adjusted; the input of the low-pass filter is connected with the output of the low-noise amplifier;
the selectable low-noise amplifier comprises a plurality of low-noise amplifiers, and a proper low-noise amplifier is selected according to an application scene.
2. The circuit of claim 1, wherein the selectable ultra-low noise amplifiers LNA1 and LNA2, wherein LNA1 is lower in equivalent input noise and narrower in bandwidth; LNA2 is wider in bandwidth and higher in equivalent input noise.
3. The circuit of claim 2, wherein the input impedance of LNA1 is ≥ 300M Ω, the unity gain bandwidth is 50MHz, and the input bias current is ≤ 30 nA; the input impedance of the LNA2 is more than or equal to 1013 omega, the unit gain bandwidth is 1MHz, and the input bias current is less than or equal to 1 pA.
4. The circuit according to any one of claims 1-3, wherein the T-type feedback network adopts a structure of resistor + resistor, and the three resistors have dynamically adjustable values according to the application.
5. The circuit according to any one of claims 1-3, wherein the zero compensation network is a series arrangement of "resistor + capacitor".
6. A circuit according to any one of claims 1 to 3, wherein the low pass filter is of MFP type low pass filtering topology with a cut-off frequency of not more than 1 MHz.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202111544399.6A CN114448362A (en) | 2021-12-16 | 2021-12-16 | Current signal amplifying circuit suitable for multi-scene requirements |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202111544399.6A CN114448362A (en) | 2021-12-16 | 2021-12-16 | Current signal amplifying circuit suitable for multi-scene requirements |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN204578469U (en) * | 2015-06-03 | 2015-08-19 | 山西中科华仪科技有限公司 | The T-shaped network automatic growth control pre-amplification circuit of photodiode |
| CN106385241A (en) * | 2016-09-19 | 2017-02-08 | 中国科学院合肥物质科学研究院 | High-sensitivity current amplifier applicable to fusion reactor strong electromagnetic environment |
| CN112165306A (en) * | 2020-12-02 | 2021-01-01 | 深圳市南方硅谷半导体有限公司 | Switching circuit of multiple gain low noise amplifier |
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2021
- 2021-12-16 CN CN202111544399.6A patent/CN114448362A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN204578469U (en) * | 2015-06-03 | 2015-08-19 | 山西中科华仪科技有限公司 | The T-shaped network automatic growth control pre-amplification circuit of photodiode |
| CN106385241A (en) * | 2016-09-19 | 2017-02-08 | 中国科学院合肥物质科学研究院 | High-sensitivity current amplifier applicable to fusion reactor strong electromagnetic environment |
| CN112165306A (en) * | 2020-12-02 | 2021-01-01 | 深圳市南方硅谷半导体有限公司 | Switching circuit of multiple gain low noise amplifier |
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