A preamplifier capable of processing bipolar signals

Abstract

The present invention discloses a preamplifier capable of processing bipolar signals, characterized in that it comprises a core amplifier circuit and a feedback circuit; wherein the core amplifier circuit comprises a common-source common-gate amplifier (1) as an input stage, a source follower (3) as a second stage, a bias circuit (4), a first bias current source (2), a second bias current source (5) and a third bias current source (6); the input stage is connected in parallel to the first bias current source (2) to increase the working current of the input stage; a feedback capacitor is connected between the input stage and the second stage to adjust the closed-loop gain of the preamplifier; the bias circuit (4) is connected to the input stage to provide a bias voltage for a common-gate transistor of the common-source common-gate amplifier (1); and the feedback circuit comprises an equivalent feedback resistor branch (7) for discharging the charge of the integrated voltage of the feedback capacitor and an equivalent feedback inductor branch (8) for absorbing the input leakage current of the reflux preamplifier.

Description

Technical Field

[0001] The invention belongs to the technical field of electronics and relates to a preamplifier capable of processing bipolar signals. Background Art

[0002] In our daily production and scientific research, we often need to receive weak voltage signals from signal sources. At this time, we need to use a preamplifier to perform a first-level pre-amplification process to improve the signal-to-noise ratio of the circuit, and then send it to the next-level circuit for the next step of signal processing under the premise of ensuring low noise. For example, in common audio amplifiers, the sound signal picked up by the microphone is usually weak, and it needs to be amplified to a certain level before it can be passed to the next level circuit; in addition, in scientific research, the readout system of high-energy physics experiments and other nuclear radiation measurements, the signal output by the detector is often relatively small, and it needs to be amplified before measurement, so the output signal of the detector is often processed by the preamplifier before being transmitted to the next level circuit. Therefore, the preamplifier circuit is an essential component of weak signal processing in electronics.

[0003] With the continuous updating and iteration of integrated circuit manufacturing processes, the operating voltage of its circuits is also constantly decreasing. For example, it has been reduced to 1.2V and below at advanced process nodes such as 130nm. The too low power supply voltage poses a great challenge to the dynamic range of the circuit. Therefore, limited by the power supply voltage, the preamplifier circuit will only perform directional optimization design for a specific polarity signal, such as adjusting the circuit operating point for the negative polarity input signal to adapt it to a larger input dynamic range, optimizing the noise performance and designing the compensation structure for the leakage current, etc. This also makes it difficult for the preamplifier circuit to take into account the pre-amplification of two polarity input signals, because the excessive swing of the input signal will cause the DC operating point of the amplifier circuit to change, and then lose the saturation amplification characteristics. This leads to the limitation of the application scope of the existing preamplifier circuit, that is, it can only be applied to the case of positive polarity input signals or negative polarity input signals, and there are great application limitations. In addition, if the performance index requirements for various aspects of the preamplifier circuit remain unchanged, but the input signal is changed from a positive swing to a negative swing, then the core circuit structure is similar or even remains consistent to a large extent, and only the feedback structure of the circuit is adjusted and optimized accordingly. Based on this premise, in order to adapt to processing input signals of two polarities, two preamplifier circuits with similar core circuit structures and slightly different feedback structures are designed, which will cause a huge waste of design resources and manpower costs. Summary of the invention

[0004] In view of the technical problems existing in the prior art, the purpose of the present invention is to provide a preamplifier circuit that can process bipolar signals. It is a preamplifier circuit for weak signal reading. While ensuring the low noise performance of the preamplifier circuit, it can also realize the amplification function of compatible processing of positive and negative polarity input signals, and is used for weak signal measurement.

[0005] The technical solution of the present invention is:

[0006] A preamplifier capable of processing bipolar signals, characterized in that it comprises a core amplifier circuit and a feedback circuit; wherein the core amplifier circuit comprises a common-source common-gate amplifier 1 as an input stage, a source follower 3 as a second stage, a bias circuit 4, a first bias current source 2, a second bias current source 5 and a third bias current source 6; the input stage is connected in parallel to the first bias current source 2 to increase the working current of the input stage and improve the voltage gain; a feedback capacitor is connected between the input stage and the second stage to adjust the closed-loop gain of the preamplifier; the bias circuit 4 is connected to the input stage to provide a bias voltage for the common-gate transistor of the common-source common-gate amplifier 1 to ensure that it works in the amplification region; the second bias current source 5 and the third bias current source 6 are respectively connected to the bias circuit 4, the third bias current source 6 is used to provide a bias current for the common-source common-gate amplifier 1, the second bias current source 5 is used to provide a bias current for the bias circuit 4, and the bias circuit 4 is used to provide a bias voltage for the common-source common-gate amplifier 1;

[0007] The feedback circuit includes an equivalent feedback resistance branch 7 and an equivalent feedback inductance branch 8; wherein the equivalent feedback resistance branch 7 is connected to the source follower 3 and the bias circuit 4 respectively, and is used to discharge the charge of the integral voltage of the feedback capacitor so that the output of the preamplifier returns to the baseline; the equivalent feedback inductance branch 8 is used to absorb the input leakage current of the reflux preamplifier so that it does not flow through the equivalent feedback resistance branch 7.

[0008] Furthermore, the equivalent feedback resistance branch 7 includes transistors M10 and M11, and the equivalent feedback inductance branch 8 includes transistors M13 and M15; the gate G10 of the transistor M10 is connected to a reference voltage source V ref The source S10 is connected to the source of the transistor M11, the drain D10 is connected to the drain D13 of the transistor M13, the drain D11 of the transistor M11 is connected to the gate G15 of the transistor M15 and the gate G13 of the transistor M13 respectively; the source S13 of the transistor M13 is connected to the drain D15 of the transistor M15, the source S15 and the source S14 of the transistor M14; the drain D14 of the transistor M14 is connected to the drain D11 of the transistor M11, and the gate G14 of the transistor M14 is connected to a reference voltage source V kn The gate G12 of transistor M12 is connected to a reference voltage source Vkp The drain D12 is connected to the source S10 of the transistor M10, the source S12 of the transistor M12, the source follower 3, and the bias circuit 4 are respectively connected to the external power supply VDD; the drain D10 and the drain D13 are respectively connected to the signal input terminal.

[0009] Furthermore, the feedback inductance L of the equivalent feedback inductance branch 8 is f =2C1 / (gm2gm4); wherein gm2 is the transconductance of transistor M11, gm4 is the transconductance of transistor M13, and C1 is the equivalent capacitance of M15.

[0010] Furthermore, the transconductance of the transistor M13 satisfies (C1 / gm4)>(2C0 / gm2); C0 is the capacitance value of the feedback capacitor.

[0011] Further, the common-source common-gate amplifier 1 includes transistors M1 and M2, the first bias current source 2 includes a transistor M7, the source follower 3 includes transistors M8 and M9, the bias circuit 4 includes transistors M3 and M4, the second bias current source 5 includes a transistor M5, and the third bias current source 6 includes a transistor M6; wherein the gate G1 of the transistor M1 is used to receive an input signal, the gate G1 is connected to the gate G9 of the transistor M9 via the feedback capacitor, and the drain D1 of the transistor M1 is connected to the gate G3 of the transistor M3 and the source G1 of the transistor M2 respectively. The gate S2 of the transistor M1 is connected to the drain D7 of the transistor M7; the source S1 of the transistor M1, the source S3 of the transistor M3, and the source S8 of the transistor M8 are respectively connected to the source S12 of the transistor M12 for receiving the voltage VDD; the gate G2 of the transistor M2 is respectively connected to the drain D3 of the transistor M3, the drain D4 of the transistor M4, and the gate G4 of the transistor M4; the source S4 of the transistor M4 is connected to the drain D5 of the transistor M5, and the gate G5 of the transistor M5, the gate G6 of the transistor M6, and the gate G7 of the transistor M7 are all connected to a reference voltage source V n The source S5 of transistor M5, the source S6 of transistor M6, and the source S7 of transistor M7 are respectively connected to the drain D9 of transistor M9; the drain D6 of transistor M6 is respectively connected to the drain D2 of transistor M2 and the gate G9 of transistor M9; the source S9 of transistor M9 is connected to the drain D8 of transistor M8 and the gate G11 of transistor M11, and the source S9 of transistor M9 serves as a signal output terminal; the gate G8 of transistor M8 is connected to a reference voltage source V p connect.

[0012] Furthermore, the transistors M1, M2, M3, M8, M9, M10, M11, and M12 are PMOS transistors, respectively, and the transistors M4, M5, M6, M7, M13, M14, and M15 are NMOS transistors, respectively.

[0013] Furthermore, the gate lengths of transistors M5 , M6 , and M7 are equal.

[0014] Furthermore, the transistors M10 and M11 are a differential pair of transistors.

[0015] Furthermore, the capacitance value of the feedback capacitor is in the order of fF.

[0016] Compared with the prior art, the present invention has the following positive effects:

[0017] The preamplifier circuit provided by the present invention can process both positive polarity signals and negative polarity signals, that is, when the application field of positive polarity signals is changed to the application field of negative polarity signals, the circuit can still work normally, complete low-noise amplification of the input signal, and generate an expected output voltage signal.

[0018] The present invention uses a circuit structure to realize processing and amplification of positive and negative polarity signals, thereby greatly expanding the application range of the preamplifier circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is the overall structural schematic diagram of the preamplifier circuit.

[0020] Figure 2 It is the core circuit of the preamplifier of the present invention.

[0021] Figure 3 It is the feedback structure of the preamplifier circuit.

[0022] Among them, 1 is a common-source and common-gate amplifier, 2 is a first bias current source, 3 is a source follower, 4 is a bias circuit, 5 is a second bias current source, 6 is a third bias current source, 7 is an equivalent feedback resistance branch, and 8 is an equivalent feedback inductance branch. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below with reference to the accompanying drawings.

[0024] The overall structural principle diagram of the preamplifier circuit of the present invention is as follows: Figure 1As shown, it mainly includes two parts: the core amplifier circuit and the feedback circuit. The essence of the core amplifier circuit is transconductance amplification, that is, realizing the amplification of voltage to current signal, and the feedback circuit is the most critical part of the present invention. Thanks to the differential feedback structure in the feedback circuit, that is, the two signal branches adjust the input and output signals at the same time, including the optimization of the circuit DC operating point and the compensation of leakage current, the core amplifier circuit in the present invention can realize the amplification of positive and negative bipolar signals. The common gate bias of the common source and common gate circuit can be realized by other bias circuits; the core amplifier circuit can be realized by using folded common source and common gate or other single-stage amplifier structures; it can also be realized by changing the types of certain transistors in the circuit.

[0025] The specific circuit implementation of the present invention is as follows Figure 2 As shown, Figure 2 The core circuit of the preamplifier is shown in the figure, where M1, M2, M3, M8, and M9 are PMOS transistors, and M4 to M7 are NMOS transistors. The working power supply voltage of the circuit is 1.2V (i.e., VDD = 1.2V, provided by an external power supply). First, the input stage is an amplifier circuit with a common source and common gate structure, and the input tube is a PMOS transistor, which is mainly used to reduce the noise of the input stage and improve the signal-to-noise ratio of the circuit; then the input stage is connected in parallel with a current source circuit to increase the working current of the input stage and improve the voltage gain; the second stage is a source follower implemented by a PMOS transistor, which is mainly used to improve the driving ability of the amplifier circuit and reduce the load influence of the subsequent stage circuit on the circuit, playing a role of buffer isolation; the feedback capacitor C0 between the first-stage input tube and the second-stage input tube is used to adjust the closed-loop gain of the preamplifier, which can be adjusted accordingly according to the dynamic range of the input signal, and its capacitance value is generally in the order of fF (i.e., 10 -15 F, F is the unit of capacitance, Farad).

[0026] Figure 2 The leftmost part shown in the figure is the bias circuit, which mainly provides bias voltage for the common gate tube of the first stage amplifier circuit (i.e., input stage) to ensure that it works in the amplification area; the three current sources at the bottom of the circuit are used to provide bias current, i.e., the first bias current source, the second bias current source, and the third bias current source, which are all implemented with NMOS type transistors, and the gate lengths of the three transistors M5, M6, and M7 are equal, which is to better match the current mirror and reduce the mismatch current. Vn and Vp are both provided by external voltage sources, where Vn = 325mV, used to provide bias voltage for M5, M6, and M7 tubes; Vp = 785mV, used to provide bias voltage for M8.

[0027] Feedback circuit such as Figure 3As shown, a differential feedback circuit is adopted, wherein M10, M11, and M12 are PMOS transistors respectively, and M13, M14, and M15 are NMOS transistors respectively; M10 and M11 in the circuit are differential pair transistors, wherein the M10 transistor is used to set the DC working reference voltage of the circuit. By adjusting the reference voltage, the DC working point can be shifted accordingly for the positive and negative polarity input signals, so that the dynamic range of the circuit can still ensure unipolar optimization; wherein the branch from the input node to the output node via the M10 and M11 transistors can be equivalent to a feedback resistor R f =2 / gm1, used to discharge the integrated voltage of the feedback capacitor of the amplifier, so that the output of the amplifier can quickly return to the baseline, where gm1 is the transconductance of the M10 tube. Therefore, the output pulse width of the preamplifier circuit mainly depends on the differential bias current of the feedback structure, that is, the working current of the M12 tube, and the size of the tube working current is adjusted by the gate voltage Vkp; Vkp = 880mV, provided by an external voltage source. This branch can optimize the circuit DC operating point for positive and negative polarity signals, that is, the circuit operating point is changed by the gate voltage Vref of the M1 tube, so that the swing input signals of both polarities are better processed and amplified; Vref = 600mV, provided by an external voltage source.

[0028] The other branch of the feedback structure is used for leakage current compensation, where the M15 tube is equivalent to an integrating capacitor C1. The voltage signal obtained by integrating the current flowing through the M11 tube on the capacitor C1 further controls the current of the M13 tube. In this way, this branch can be equivalent to a feedback inductor L between the input and output. f =2C1 / (gm2gm4), so the input leakage current of the circuit can be absorbed and refluxed by this branch without flowing through the equivalent feedback resistance branch, and both positive and negative leakage currents can be absorbed by this branch, so that the circuit can be compatible with processing leakage current signals of both positive and negative polarity signals, ensuring the normal operation of the charge sensitive preamplifier core circuit. In addition, in order to ensure the normal and stable operation of the circuit, the transconductance of the M13 tube needs to satisfy (C1 / gm4)>(2C0 / gm2), where C1 is the equivalent capacitance of M15, C0 is the feedback capacitance of the preamplifier core circuit, and gm2 and gm4 are the transconductances of the M11 tube and the M13 tube respectively.

[0029] Figure 3 The IN and OUT ports in Figure 2 The IN and OUT ports in are connected separately, that is, Figure 2 and Figure 3The input signal in the same node is the same node, and the output signal is also the same node. The gate of M1 tube is used to receive the input signal, and is connected to the drain of M10 and the drain of M13 to receive the input signal; the gate of M11, the drain of M8 and the source of M9 are connected, and the source of M9 is used as the signal output terminal. VSS represents the ground potential, and VDD represents the power supply voltage (powered by an external power supply). The input signal corresponds to Figure 2 and Figure 3 The output signal corresponds to the IN terminal of Figure 2 and Figure 3 OUT terminal in.

[0030] In summary, the above are only some implementation schemes of the present invention, and are not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preamplifier capable of processing bipolar signals, characterized in that: Including core amplifier circuit and feedback circuit; in The core amplifier circuit comprises a common-source common-gate amplifier (1) as an input stage, a source follower (3) as a second stage, a bias circuit (4), a first bias current source (2), a second bias current source (5) and a third bias current source (6); The input stage is connected in parallel to the first bias current source (2) to increase the working current of the input stage and improve the voltage gain; a feedback capacitor is connected between the input stage and the second stage to adjust the closed-loop gain of the preamplifier; the bias circuit (4) is connected to the input stage to provide a bias voltage for the common-gate transistor of the common-source common-gate amplifier (1) to ensure that it works in the amplification region; the second bias current source (5) and the third bias current source (6) are respectively connected to the bias circuit (4), the third bias current source (6) is used to provide a bias current for the common-source common-gate amplifier (1), the second bias current source (5) is used to provide a bias current for the bias circuit (4), and the bias circuit (4) is used to provide a bias voltage for the common-source common-gate amplifier (1); The feedback circuit comprises an equivalent feedback resistance branch (7) and an equivalent feedback inductance branch (8); wherein the equivalent feedback resistance branch (7) is respectively connected to the source follower (3) and the bias circuit (4) and is used to discharge the charge of the integrated voltage of the feedback capacitor so that the output of the preamplifier returns to the baseline; The equivalent feedback inductor branch (8) is used to absorb the input leakage current of the reflux preamplifier so that it does not flow through the equivalent feedback resistor branch (7); The equivalent feedback resistance branch (7) includes transistors M10 and M11, and the equivalent feedback inductance branch (8) includes transistors M13 and M15; the gate G10 of the transistor M10 is connected to a reference voltage source V ref The source S10 is connected to the source of the transistor M11, the drain D10 is connected to the drain D13 of the transistor M13, and the drain D11 of the transistor M11 is connected to the gate G15 of the transistor M15 and the gate G13 of the transistor M13 respectively; The source S13 of the transistor M13 is connected to the drain D15 of the transistor M15, the source S15 and the source S14 of the transistor M14; the drain D14 of the transistor M14 is connected to the drain D11 of the transistor M11, and the gate G14 of the transistor M14 is connected to a reference voltage source V kn The gate G12 of transistor M12 is connected to a reference voltage source V kp The drain D12 is connected to the source S10 of the transistor M10, the source S12 of the transistor M12, the source follower (3), and the bias circuit (4) are respectively connected to the external power supply VDD; the drain D10 and the drain D13 are respectively connected to the signal input terminal.

2. The preamplifier capable of processing bipolar signals as claimed in claim 1, characterized in that: The feedback inductance L of the equivalent feedback inductance branch (8) is f =2C1 / (gm2gm4); wherein gm2 is the transconductance of transistor M11, gm4 is the transconductance of transistor M13, and C1 is the equivalent capacitance of M15.

3. The preamplifier capable of processing bipolar signals as claimed in claim 2, characterized in that: The transconductance of the transistor M13 satisfies (C1 / gm4)>(2C0 / gm2); C0 is the capacitance value of the feedback capacitor.

4. The preamplifier capable of processing bipolar signals as claimed in claim 1 or 2, characterized in that: The cascode amplifier (1) comprises transistors M1 and M2, the first bias current source (2) comprises a transistor M7, the source follower (3) comprises transistors M8 and M9, the bias circuit (4) comprises transistors M3 and M4, the second bias current source (5) comprises a transistor M5, and the third bias current source (6) comprises a transistor M6; wherein a gate G1 of the transistor M1 is used to receive an input signal, the gate G1 is connected to a gate G9 of the transistor M9 via the feedback capacitor, and a drain D1 of the transistor M1 is connected to a gate G3 of the transistor M3 and a drain D2 of the transistor M4 respectively. The source S2 of transistor M2 is connected to the drain D7 of transistor M7; the source S1 of transistor M1, the source S3 of transistor M3, and the source S8 of transistor M8 are respectively connected to the source S12 of transistor M12 for receiving voltage VDD; the gate G2 of transistor M2 is respectively connected to the drain D3 of transistor M3, the drain D4 of transistor M4, and the gate G4 of transistor M4; the source S4 of transistor M4 is connected to the drain D5 of transistor M5, and the gate G5 of transistor M5, the gate G6 of transistor M6, and the gate G7 of transistor M7 are all connected to a reference voltage source V n The source S5 of transistor M5, the source S6 of transistor M6, and the source S7 of transistor M7 are respectively connected to the drain D9 of transistor M9; the drain D6 of transistor M6 is respectively connected to the drain D2 of transistor M2 and the gate G9 of transistor M9; the source S9 of transistor M9 is connected to the drain D8 of transistor M8 and the gate G11 of transistor M11, and the source S9 of transistor M9 serves as a signal output terminal; the gate G8 of transistor M8 is connected to a reference voltage source V p connect.

5. The preamplifier capable of processing bipolar signals as claimed in claim 4, characterized in that: The transistors M1, M2, M3, M8, M9, M10, M11, and M12 are PMOS transistors, respectively, and the transistors M4, M5, M6, M7, M13, M14, and M15 are NMOS transistors, respectively.

6. The preamplifier capable of processing bipolar signals as claimed in claim 5, characterized in that: The gate lengths of transistors M5, M6, and M7 are equal.

7. The preamplifier capable of processing bipolar signals as claimed in claim 5, characterized in that: The transistors M10 and M11 are a differential pair of transistors.

8. The preamplifier capable of processing bipolar signals as claimed in claim 1, characterized in that: The capacitance value of the feedback capacitor is in the order of fF.

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