A weak pulse signal amplification circuit

Abstract

This invention relates to a weak pulse signal amplification circuit, comprising six unit circuits: a detector output circuit, a first-stage charge-sensitive amplification circuit, a second-stage negative feedback amplification circuit, a current amplification circuit, a positive power supply circuit, and a negative power supply circuit. The detector output circuit, the first-stage charge-sensitive amplification circuit, the second-stage negative feedback amplification circuit, and the current amplification circuit are connected in series via coupling capacitors. The first-stage charge-sensitive amplification circuit and the second-stage negative feedback amplification circuit together constitute a two-stage voltage amplification circuit, and the voltage amplification factor of the entire circuit is the product of the individual amplification factors of the two amplification circuits. The positive and negative power supply circuits provide the operating voltage for the entire circuit. This invention's circuit can achieve both voltage and current amplification, and has advantages such as high amplification factor, wide signal bandwidth, strong load capacity, high signal-to-noise ratio, and strong anti-interference capability.

Description

Technical Field

[0001] This invention relates to a weak pulse signal amplification circuit, belonging to the field of nuclear radiation detection technology. Background Technology

[0002] Gas ionization detectors are widely used in nuclear radiation detection due to their high detection sensitivity. When the detector is irradiated by radiation, the radiation interacts with molecules in the gas, producing ion pairs consisting of an electron and a positive ion. In this case, if a DC high voltage is applied to the collecting electrode and the high-voltage electrode that constitute the detector, these electrons and positive ions will be pulled towards the positive and negative electrodes respectively under the influence of the electric field and collected. The entire collection process generates a pulse voltage signal. However, the voltage pulse signal output by the gas ionization detector is very weak, with a voltage amplitude typically on the order of microvolts (10⁻⁶). -6 V-10 -4 V), while the subsequent circuits used for counting processing (referred to as counting circuits, whose main function is to shape and digitize the signal waveform) typically require the signal amplitude to be at least on the order of volts (10). 0 (V). Obviously, such a weak voltage signal output by the detector must be amplified before it can be used in the counting circuit.

[0003] Currently, the industry standard is to package a charge-sensitive preamplifier at the signal output of a gas ionization detector to amplify weak pulse signals. However, a simple charge-sensitive preamplifier has two main drawbacks: First, the voltage amplification factor cannot be too high. When the amplification factor is too high, the signal will be affected by the finite gain-bandwidth product (GBP) generated by the operational amplifier, resulting in a smaller signal bandwidth, which limits the application of this type of amplifier circuit to some extent. Second, it has weak load capacity and poor anti-interference capabilities, and cannot achieve long-distance signal transmission. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned problems by providing a weak pulse signal amplification circuit with high amplification factor, high signal-to-noise ratio, wide bandwidth, strong anti-interference ability, and strong load capacity.

[0005] The objective of this invention is achieved as follows: a weak pulse signal amplification circuit, characterized in that it includes a detector output circuit, a two-stage voltage amplification circuit, a current amplification circuit, a positive power supply circuit, and a negative power supply circuit. The two-stage voltage amplification circuit is composed of a first-stage charge-sensitive amplification circuit and a second-stage negative feedback amplification circuit connected in series.

[0006] The detector output circuit is electrically connected to the first-stage charge-sensitive amplifier circuit in the two-stage voltage amplifier circuit; the current amplifier circuit is electrically connected to the second-stage negative feedback amplifier circuit in the two-stage voltage amplifier circuit; the detector output circuit, the first-stage charge-sensitive amplifier circuit, the second-stage negative feedback amplifier circuit, and the current amplifier circuit are connected in series through a coupling capacitor; the positive power supply circuit and the negative power supply circuit simultaneously provide operating voltage to the first-stage charge-sensitive amplifier circuit, the second-stage negative feedback amplifier circuit, and the current amplifier circuit.

[0007] The detector output circuit generates a pulse signal, which enters a two-stage voltage amplifier circuit. In the two-stage voltage amplifier circuit, the pulse signal is amplified by a first-stage charge-sensitive amplifier circuit and a second-stage negative feedback amplifier circuit. The voltage-amplified pulse signal enters a current amplifier circuit and is then amplified by the current to output a signal.

[0008] The detector output circuit includes a detector, a high-voltage DC power supply HV output terminal, a resistor R1, a capacitor C1, and a capacitor C9; wherein, the ground terminal of the detector is grounded, the signal output terminal of the detector is connected to one end of the resistor R1 and one end of the capacitor C1, the other end of the resistor R1 is connected to the high-voltage DC power supply HV output terminal and one end of the capacitor C9, and the other end of the capacitor C9 is grounded.

[0009] The first-stage charge-sensitive amplifier circuit includes a resistor R2, an operational amplifier IC1, a capacitor Cf, and a resistor R3; wherein, the other end of capacitor C1, one end of resistor R2, one end of resistor R3, and one end of capacitor Cf are all connected to the negative signal input terminal of operational amplifier IC1; the other end of resistor R2 and the positive signal input terminal of operational amplifier IC1 are grounded; the other end of resistor R3, the other end of capacitor Cf, and the signal output terminal of operational amplifier IC1 are all connected to one end of capacitor C2.

[0010] The secondary negative feedback amplifier circuit includes capacitor C2, resistor R4, resistor R5, and operational amplifier IC2; wherein, the other end of capacitor C2 is connected to one end of resistor R4, the other end of resistor R4 and one end of resistor R5 are connected to the negative signal input terminal of operational amplifier IC2, the positive signal input terminal of operational amplifier IC2 is grounded, and the other end of resistor R5 and the signal output terminal of operational amplifier IC2 are simultaneously connected to one end of capacitor C3;

[0011] The current amplification circuit includes capacitor C3, diodes D1 and D2, an NPN transistor, a PNP transistor, resistors R6, R7, R8, and R9, and capacitor C4. Diodes D1 and D2 are required to have identical characteristics, as are the NPN and PNP transistors. Resistors R6 and R7 have equal resistance values, and resistors R8 and R9 have equal resistance values. The other end of capacitor C3 is connected to the cathode of diode D1 and the anode of diode D2. The anode of diode D1 is simultaneously connected to one end of resistor R6 and the base of the NPN transistor. The emitter of the NPN transistor is connected to one end of resistor R8. The cathode of diode D2 is simultaneously connected to one end of resistor R7 and the base of the PNP transistor. The emitter of the PNP transistor is connected to one end of resistor R9. The other ends of resistors R8 and R9 are simultaneously connected to one end of capacitor C4. The other end of capacitor C4 outputs a signal.

[0012] The positive power supply circuit includes a positive power supply output terminal +VCC, an inductor L1, a capacitor C5, and a capacitor C6; the inductor L1, capacitor C5, and capacitor C6 form a "Π" type LC filter; wherein, the +VCC output terminal is connected to one end of capacitor C5 and one end of inductor L1 respectively, the other end of inductor L1 is connected to one end of capacitor C6, the positive power supply input terminal of operational amplifier IC1, the positive power supply input terminal of operational amplifier IC2, the other end of resistor R6, and the collector of transistor NPN; the other ends of capacitor C5 and capacitor C6 are both grounded;

[0013] The negative power supply circuit includes a negative power supply output terminal -VCC, an inductor L2, a capacitor C7, and a capacitor C8. The inductor L2, capacitor C7, and capacitor C8 form a "Π"-type LC filter. The -VCC output terminal is connected to one end of capacitor C7 and one end of inductor L2. The other end of inductor L2 is connected to one end of capacitor C8, the negative power supply input terminal of operational amplifier IC1, the negative power supply input terminal of operational amplifier IC2, the other end of resistor R7, and the collector of transistor PNP. The other ends of capacitor C7 and capacitor C8 are both grounded.

[0014] The operational amplifier IC1 is model AD8065.

[0015] The operational amplifier IC2 is model AD8065.

[0016] The beneficial effects of this invention are:

[0017] First, this circuit amplifies extremely weak voltage signals by connecting a first-stage charge-sensitive amplifier circuit and a second-stage negative feedback amplifier circuit in series. The amplification factor is the product of the individual amplification factors of these two modules. Therefore, the amplification factors of both the first-stage charge-sensitive amplifier circuit and the second-stage negative feedback amplifier circuit do not need to be too high. Consequently, the entire circuit is not affected by the operational amplifier's finite gain-bandwidth product (GBP) and its own open-loop gain (OLG). Furthermore, this circuit ensures that the operational amplifier's input terminal achieves high input impedance while maintaining a low level of bias. Therefore, this circuit simultaneously possesses the advantages of high amplification factor and wide bandwidth.

[0018] Secondly, the current amplification circuit in this circuit is ingeniously designed. It can not only amplify the current and ensure that the output signal is anti-interference and has a strong load capacity, thus enabling long-distance signal transmission, but also avoid waveform distortion caused by the truncation of the negative half-axis voltage waveform.

[0019] Third, this circuit not only incorporates noise filtering units in the detector output circuit, the first-stage charge-sensitive amplifier circuit, and the power supply circuit, but also adds coupling capacitors between the various amplification modules during signal transmission. These coupling capacitors can isolate DC noise mixed in with the pulse signal. Through these measures, noise is effectively reduced, and the signal-to-noise ratio (signal voltage amplitude / noise voltage amplitude) of the entire circuit is improved.

[0020] In summary, the weak pulse signal amplification circuit provided by this invention includes six unit circuits: a detector output circuit, a first-stage charge-sensitive amplification circuit, a second-stage negative feedback amplification circuit, a current amplification circuit, a positive power supply circuit, and a negative power supply circuit. The detector output circuit, the first-stage charge-sensitive amplification circuit, the second-stage negative feedback amplification circuit, and the current amplification circuit are connected in series via coupling capacitors. The first-stage charge-sensitive amplification circuit and the second-stage negative feedback amplification circuit together constitute a two-stage voltage amplification circuit, and the voltage amplification factor of the entire circuit is the product of the individual amplification factors of the two amplification factors. The positive and negative power supply circuits provide the operating voltage for the entire circuit. This invention's circuit can achieve both voltage and current amplification, and has advantages such as high amplification factor, wide signal bandwidth, strong load capacity, high signal-to-noise ratio, and strong anti-interference capability. Attached Figure Description

[0021] Figure 1 This is the circuit schematic diagram of the present invention;

[0022] Figure 2 This is a block diagram of the circuit structure.

[0023] In the diagram, 1 is the detector output circuit, 2 is the two-stage voltage amplifier circuit, 2-1 is the first-stage charge-sensitive amplifier circuit, 2-2 is the second-stage negative feedback amplifier circuit, 3 is the current amplifier circuit, 4 is the positive power supply circuit, and 5 is the negative power supply circuit. Detailed Implementation

[0024] The following will refer to the instruction manual appendix. Figure 1 The structure of the circuit of the present invention is roughly described as follows:

[0025] A weak pulse signal amplification circuit includes a detector output circuit 1, a two-stage voltage amplification circuit 2, a current amplification circuit 3, a positive power supply circuit 4, and a negative power supply circuit 5. The two-stage voltage amplification circuit 2 is composed of a first-stage charge-sensitive amplification circuit 2-1 and a second-stage negative feedback amplification circuit 2-2 connected in series. The detector output circuit 1 is connected to the first-stage charge-sensitive amplification circuit 2-1 in the two-stage voltage amplification circuit 2. The current amplification circuit 3 is connected to the second-stage negative feedback amplification circuit 2-2 in the two-stage voltage amplification circuit 2. The detector output circuit 1, the first-stage charge-sensitive amplification circuit 2-1, the second-stage negative feedback amplification circuit 2-2, and the current amplification circuit 3 are connected in series through a capacitor. The positive power supply circuit and the negative power supply circuit simultaneously provide operating voltages for the first-stage charge-sensitive amplification circuit 2-1, the second-stage negative feedback amplification circuit 2-2, and the current amplification circuit 3.

[0026] The detector output circuit 1 generates a pulse signal, which enters a two-stage voltage amplifier circuit 2. In the two-stage voltage amplifier circuit 2, the pulse signal is amplified by a first-stage charge-sensitive amplifier circuit 2-1 and a second-stage negative feedback amplifier circuit 2-2. The voltage-amplified pulse signal enters a current amplifier circuit 3 and is then amplified by the current to output a signal.

[0027] Right now:

[0028] Step 1: The pulse signal is generated by the detector output circuit 1.

[0029] Step 2: The pulse signal enters the two-stage voltage amplifier circuit 2 for voltage amplification. The two-stage voltage amplifier circuit 2 is composed of a first-stage charge-sensitive amplifier circuit 2-1 and a second-stage negative feedback amplifier circuit 2-2 connected in series. Its total voltage amplification factor is the product of the amplification factors of these two circuits.

[0030] The third step is to amplify the voltage pulse signal into the current amplifier circuit 3, and then output the signal after amplification.

[0031] Throughout the process, both positive and negative power supply circuits need to provide operating voltage to the two-stage voltage amplifier circuit and the current amplifier circuit simultaneously.

[0032] The following will refer to the instruction manual appendix. Figure 2 The principles, functions, and precautions of each unit circuit in the circuit of this invention are described in detail below:

[0033] A weak pulse signal amplification circuit is characterized by comprising a detector output circuit, a first-stage charge-sensitive amplification circuit, a second-stage negative feedback amplification circuit, a current amplification circuit, a positive power supply circuit, and a negative power supply circuit, which can achieve both voltage amplification and current amplification.

[0034] The detector output circuit comprises a detector, a high-voltage DC power supply HV output terminal, a resistor R1, a capacitor C1, and a capacitor C9. Specifically: the detector ground terminal is grounded; the signal output terminal is connected to one end of resistor R1 and one end of capacitor C1; the other end of resistor R1 is connected to the high-voltage DC power supply HV output terminal and one end of capacitor C9; and the other end of capacitor C9 is grounded.

[0035] The first-stage charge-sensitive amplifier circuit comprises a resistor R2, an operational amplifier IC1 (model AD8065, amplification factor A0), a capacitor Cf, and a resistor R3. Specifically: the other end of capacitor C1, one end of resistor R2, one end of resistor R3, and one end of capacitor Cf are all connected to the negative signal input terminal of operational amplifier IC1. The other end of resistor R2 and the positive signal input terminal of operational amplifier IC1 are grounded. The other end of resistor R3, the other end of capacitor Cf, and the signal output terminal of operational amplifier IC1 are all connected to one end of capacitor C2.

[0036] The two-stage negative feedback amplifier circuit includes capacitor C2, resistors R4 and R5, and operational amplifier IC2 (model AD8065, amplification factor A0). Specifically: the other end of capacitor C2 is connected to one end of resistor R4; the other end of resistor R4 and one end of resistor R5 are connected to the negative signal input terminal of operational amplifier IC2; the positive signal input terminal of operational amplifier IC2 is grounded; and the other end of resistor R5 and the signal output terminal of operational amplifier IC2 are simultaneously connected to one end of capacitor C3.

[0037] The current amplification circuit comprises capacitor C3, diodes D1 and D2, an NPN transistor, a PNP transistor, resistors R6, R7, R8, and R9, and capacitor C4. Diodes D1 and D2 must have identical characteristics, as must the NPN and PNP transistors. Resistors R6 and R7, and R8 and R9, must have equal resistance values. The other end of capacitor C3 is connected to the cathode of diode D1 and the anode of diode D2. The anode of diode D1 is connected to one end of resistor R6 and the base of the NPN transistor. The emitter of the NPN transistor is connected to one end of resistor R8. The cathode of diode D2 is connected to one end of resistor R7 and the base of the PNP transistor. The emitter of the PNP transistor is connected to one end of resistor R9. The other ends of resistors R8 and R9 are connected to one end of capacitor C4. The other end of capacitor C4 outputs the signal.

[0038] The positive power supply circuit comprises a positive power supply output terminal +VCC, an inductor L1, a capacitor C5, and a capacitor C6. The inductor L1, capacitor C5, and capacitor C6 form a "Π"-type LC filter. The +VCC output terminal is connected to one end of capacitor C5 and one end of inductor L1. The other end of inductor L1 is simultaneously connected to one end of capacitor C6, the positive power supply input terminal of operational amplifier IC1, the positive power supply input terminal of operational amplifier IC2, the other end of resistor R6, and the collector of the NPN transistor. The other ends of capacitors C5 and C6 are both grounded.

[0039] The negative power supply circuit comprises a negative power supply output terminal -VCC, inductor L2, capacitor C7, and capacitor C8. Inductor L2, capacitor C7, and capacitor C8 form a "Π"-type LC filter, wherein: the -VCC output terminal is connected to one end of capacitor C7 and one end of inductor L2 respectively; the other end of inductor L2 is simultaneously connected to one end of capacitor C8, the negative power supply input terminal of operational amplifier IC1, the negative power supply input terminal of operational amplifier IC2, the other end of resistor R7, and the collector of the PNP transistor; the other ends of capacitors C7 and C8 are both grounded.

[0040] According to the instruction manual Figure 2 In the detector output circuit, the detector's operating voltage is provided by a high-voltage DC power supply HV. For the pulse signal generated by the detector, since resistor R1 has a high impedance and capacitor C1 has a low impedance, it can be approximated that the pulse signal will only enter the subsequent charge-sensitive amplifier circuit through capacitor C1. Capacitor C1 acts as a signal coupler, isolating the DC voltage HV while allowing the pulse signal to pass through. Resistor R1 and capacitor C9 form an RC low-pass filter, preventing low-frequency noise generated by the high-voltage DC power supply module from entering the first-stage charge-sensitive amplifier circuit.

[0041] According to the instruction manual Figure 2 In the first-stage charge-sensitive amplifier circuit, capacitor C1 and resistor R2 together form a CR high-pass filter. By selecting appropriate capacitor C1 and resistor R2, pulse signals above the filter's cutoff frequency can be allowed to pass through, while noise below the cutoff frequency is blocked from entering the amplifier. Capacitor Cf represents the feedback capacitor, and its value directly determines the amplification factor of the entire charge-sensitive amplifier circuit. The detailed derivation process is as follows:

[0042] Assume that the amplification factor of operational amplifier IC1 is A0, the total capacitance at the input terminal is C, the voltage signal generated at the input terminal of operational amplifier IC1 is Usr, and the average charge generated by the detector is Q.

[0043] When the current signal passes through capacitor C1, since the input impedance of operational amplifier IC1 is very high, it can be approximated that the current will not pass through operational amplifier IC1, but will pass through capacitor Cf and charge it.

[0044] C=(1+A0)Cf (1)

[0045] The voltage signal Usr generated at the input terminal of operational amplifier IC1 is

[0046]

[0047] Because the amplification factor (A0) of operational amplifier IC1 is much greater than 1, then

[0048]

[0049] Because operational amplifier IC1 is connected with negative feedback, the amplifier's output voltage signal U sc for

[0050]

[0051] As shown in equation (4), the voltage pulse signal Usc output by the amplifier is proportional to the charge Q generated by the detector, and is independent of the amplification factor A0 of the operational amplifier. Since the unit charge generated by the detector can output a voltage amplitude of Usc = -1 / Cf through the amplifier, this voltage is called the charge-sensitive voltage, and we call the amplifier a charge-sensitive amplifier. Its voltage amplification factor is 1 / Cf, so we can change the amplification factor of the charge-sensitive amplifier circuit by changing the value of Cf.

[0052] Resistor R3 is used to discharge the charge stored in capacitor Cf. When a pulse signal current charges Cf, the charge in Cf must be quickly released to allow the next signal current to charge it. Otherwise, two consequences will occur: first, the capacitor will be continuously charged, and if the charge is not released, Cf will break down; second, different pulse signals will accumulate, leading to signal buildup. Due to the presence of resistor R3, the charge stored in Cf can be quickly released through the parallel resistor R3, thus ensuring that Usc returns to zero. The time constant T = R3Cf formed by resistor R3 and capacitor Cf determines the charge release rate in capacitor Cf. The smaller the time constant T, the faster the charging and discharging speed. Since 1 / Cf determines the amplification factor of the charge-sensitive amplifier circuit, the value of Cf should be small. However, the value of resistor R3 cannot be too small; otherwise, the excessively fast discharge speed will affect the charging of capacitor Cf by the signal current. Therefore, resistor R3 cannot be too small or too large.

[0053] If only a single-stage charge-sensitive amplifier circuit is used, when the voltage amplification factor is too large, the pulse signal will be affected by the finite gain-bandwidth product (GBP) of the operational amplifier, resulting in a smaller pulse width. Therefore, the amplification factor -1 / Cf of the charge-sensitive amplifier circuit cannot be too large. To solve this problem, this invention connects a two-stage negative feedback amplifier circuit in series after the first-stage charge-sensitive amplifier.

[0054] According to the instruction manual Figure 2 In a two-stage negative feedback amplifier circuit, the amplification factor is determined by resistors R4 and R5, and its amplification factor is -R5 / R4. Resistor C2 serves to couple the signal, i.e., isolate DC noise signals while allowing pulse signals to pass through.

[0055] As described above, after the pulse signal is amplified by two stages, the total voltage amplification factor is (-1 / Cf)*(-R5 / R4). To ensure that the pulse voltage signal has sufficient anti-interference capability and load capacity to achieve long-distance transmission of the pulse signal, this invention connects a current amplifier circuit in series after the two-stage negative feedback circuit.

[0056] Typically, current amplification can be achieved using an emitter follower mainly composed of NPN transistors, which offers advantages such as high input impedance, low output impedance, and strong load-driving capability. However, due to the emitter load resistor, when the output current is large (i.e., the impedance is low), the negative half-axis of the output waveform is truncated, preventing the acquisition of the complete maximum output voltage and resulting in signal distortion. To improve performance and mitigate this drawback, in engineering practice, the emitter load resistor is usually replaced with a PNP transistor to form a conventional push-pull emitter follower.

[0057] However, this invention makes the following optimizations and improvements to this conventional push-pull emitter follower:

[0058] According to the instruction manual Figure 2 In the current amplifier circuit, diodes D1 and D2 have identical characteristics. The characteristics of NPN and PNP transistors must also be identical; resistors R6 and R7 have the same value, as do resistors R8 and R9. Resistors R6 and R7 are the base bias resistors for the NPN and PNP transistors, respectively, while resistors R8 and R9 are the emitter resistors for the NPN and PNP transistors, respectively. Capacitors C3 and C4 are used for signal coupling, i.e., isolating DC noise while allowing pulse signals to pass through. Resistors R6 and R7 ensure that the DC bias voltage at the signal input of the current amplifier circuit is 0 volts. Resistors R8 and R9, as emitter resistors, ensure that the DC bias voltage at the signal output of the current amplifier circuit is 0 volts and limit current to prevent thermal breakdown of the transistor due to excessive current. Due to the introduction of R8 and R9, the output impedance of the entire current amplifier is not 0 ohms. In order to ensure a low impedance, the resistance values ​​of resistors R8 and R9 should not be too large. It is sufficient to ensure that the collector current of the transistor is about 10mA.

[0059] The function of diodes D1 and D2 is to eliminate waveform distortion caused by the transistor. The specific analysis is as follows: Without diodes D1 and D2, the base potentials of the NPN and PNP transistors are the same. When the output signal is 0 volts, there is no potential difference between the base and emitter, and no current is generated at the base. If the transistor is in the cutoff region and stops working, it will cause signal switching distortion. The transistor can only work when the base potential of the NPN transistor is about 0.6V higher than the emitter potential. Since a crystal diode has a forward voltage drop of about 0.6V, when diodes D1 and D2 are introduced into the circuit, this approximately 0.6V forward voltage drop can be used as the compensation voltage for the transistor, thereby eliminating signal switching distortion.

[0060] According to the instruction manual Figure 2 The positive and negative power supply circuits are designed to provide DC operating voltage to the entire amplifier circuit. The absolute values ​​of the positive and negative power supply voltages must be equal. This invention designs a "Π"-type LC filter consisting of an inductor and two capacitors at the ±VCC output terminal to eliminate AC noise from the ±VCC power supply from entering the signal transmission channel and improve the circuit signal-to-noise ratio.

Claims

1. A weak pulse signal amplification circuit, characterized in that: It includes a detector output circuit (1), a two-stage voltage amplifier circuit (2), a current amplifier circuit (3), a positive power supply circuit (4), and a negative power supply circuit (5). The two-stage voltage amplifier circuit (2) is composed of a first-stage charge-sensitive amplifier circuit (2-1) and a second-stage negative feedback amplifier circuit (2-2) connected in series. The detector output circuit (1) is electrically connected to the first-stage charge-sensitive amplifier circuit (2-1) in the two-stage voltage amplifier circuit (2); the current amplifier circuit (3) is connected to the second-stage negative feedback amplifier circuit (2-2) in the two-stage voltage amplifier circuit (2); the detector output circuit (1), the first-stage charge-sensitive amplifier circuit (2-1), the second-stage negative feedback amplifier circuit (2-2), and the current amplifier circuit (3) are connected in series through a capacitor; the positive power supply circuit and the negative power supply circuit simultaneously provide operating voltage to the first-stage charge-sensitive amplifier circuit (2-1), the second-stage negative feedback amplifier circuit (2-2), and the current amplifier circuit (3); The detector output circuit (1) generates a pulse signal, which enters a two-stage voltage amplifier circuit (2). The pulse signal is amplified in the two-stage voltage amplifier circuit (2) by passing through a first-stage charge-sensitive amplifier circuit (2-1) and a second-stage negative feedback amplifier circuit (2-2). The voltage-amplified pulse signal enters a current amplifier circuit (3) and is output after current amplification. The detector output circuit includes a detector, a high-voltage DC power supply HV output terminal, a resistor R1, a capacitor C1, and a capacitor C9; wherein, the ground terminal of the detector is grounded, the signal output terminal of the detector is connected to one end of the resistor R1 and one end of the capacitor C1, the other end of the resistor R1 is connected to the high-voltage DC power supply HV output terminal and one end of the capacitor C9, and the other end of the capacitor C9 is grounded. The first-stage charge-sensitive amplifier circuit includes a resistor R2, an operational amplifier IC1, a capacitor Cf, and a resistor R3. The other end of capacitor C1, one end of resistor R2, one end of resistor R3, and one end of capacitor Cf are all connected to the negative signal input terminal of operational amplifier IC1. The other end of resistor R2 and the positive signal input terminal of operational amplifier IC1 are grounded. The other end of resistor R3, the other end of capacitor Cf, and the signal output terminal of operational amplifier IC1 are all connected to one end of capacitor C2. The secondary negative feedback amplifier circuit includes capacitor C2, resistor R4, resistor R5, and operational amplifier IC2; wherein, the other end of capacitor C2 is connected to one end of resistor R4, the other end of resistor R4 and one end of resistor R5 are connected to the negative signal input terminal of operational amplifier IC2, the positive signal input terminal of operational amplifier IC2 is grounded, and the other end of resistor R5 and the signal output terminal of operational amplifier IC2 are simultaneously connected to one end of capacitor C3; The current amplification circuit includes capacitor C3, diodes D1 and D2, an NPN transistor, a PNP transistor, resistors R6, R7, R8, and R9, and capacitor C4. Diodes D1 and D2 are required to have identical characteristics, as are the NPN and PNP transistors. Resistors R6 and R7 have equal resistance values, and resistors R8 and R9 have equal resistance values. The other end of capacitor C3 is connected to the negative terminal of diode D1 and the positive terminal of diode D2. The positive terminal of diode D1 is also connected to one end of resistor R6 and the base of NPN transistor. The emitter of NPN transistor is connected to one end of resistor R8. The negative terminal of diode D2 is also connected to one end of resistor R7 and the base of PNP transistor. The emitter of PNP transistor is connected to one end of resistor R9. The other ends of resistor R8 and resistor R9 are simultaneously connected to one end of capacitor C4. The other end of capacitor C4 outputs a signal. The positive power supply circuit includes a positive power supply output terminal +VCC, an inductor L1, a capacitor C5, and a capacitor C6; the inductor L1, capacitor C5, and capacitor C6 form a "Π" type LC filter; wherein, the +VCC output terminal is connected to one end of capacitor C5 and one end of inductor L1 respectively, the other end of inductor L1 is connected to one end of capacitor C6, the positive power supply input terminal of operational amplifier IC1, the positive power supply input terminal of operational amplifier IC2, the other end of resistor R6, and the collector of transistor NPN; the other ends of capacitor C5 and capacitor C6 are both grounded; The negative power supply circuit includes a negative power supply output terminal -VCC, an inductor L2, a capacitor C7, and a capacitor C8. The inductor L2, capacitor C7, and capacitor C8 form a "Π" type LC filter. The -VCC output terminal is connected to one end of capacitor C7 and one end of inductor L2, respectively. The other end of inductor L2 is connected to one end of capacitor C8, the negative power supply input terminal of operational amplifier IC1, the negative power supply input terminal of operational amplifier IC2, the other end of resistor R7, and the collector of transistor PNP. The other ends of capacitor C7 and capacitor C8 are both grounded. In the first-stage charge-sensitive amplifier circuit, capacitor C1 and resistor R2 together form a CR high-pass filter. By selecting appropriate capacitor C1 and resistor R2, pulse signals higher than the cutoff frequency of this filter can be allowed to pass through, while noise below the cutoff frequency is blocked from entering the amplifier. Capacitor Cf represents the feedback capacitor, and its value directly determines the amplification factor of the entire charge-sensitive amplifier circuit. The detailed derivation process is as follows: Assume that the amplification factor of operational amplifier IC1 is A0, the total capacitance at the input terminal is C, the voltage signal generated at the input terminal of operational amplifier IC1 is Usr, and the average charge generated by the detector is Q. When the current signal passes through capacitor C1, since the input impedance of operational amplifier IC1 is very high, it can be approximated that the current will not pass through operational amplifier IC1, but will pass through capacitor Cf and charge it; then C=(1+A0)Cf (1) The voltage signal Usr generated at the input terminal of operational amplifier IC1 is Because the amplification factor (A0) of operational amplifier IC1 is much greater than 1, then Since operational amplifier IC1 is connected with negative feedback, the amplifier's output voltage signal Usc is As can be seen from equation (4), the voltage pulse signal Usc output by the amplifier is proportional to the charge Q generated by the detector, and is independent of the amplification factor A0 of the operational amplifier. Because the unit charge generated by the detector can output a voltage amplitude of Usc = -1 / Cf through the amplifier, this voltage is called the charge-sensitive voltage. We call the amplifier a charge-sensitive amplifier, and its voltage amplification factor is 1 / Cf. Therefore, we can change the amplification factor of the charge-sensitive amplifier circuit by changing the value of Cf. Resistor R3 is used to discharge the charge stored in capacitor Cf. When a pulse signal current charges Cf, the charge in Cf must be released quickly so that the next signal current can continue to charge it. Otherwise, the following two consequences will occur: first, the capacitor will be continuously charged, and if the charge is not released, Cf will break down; second, different pulse signals will accumulate, leading to signal buildup. Due to the presence of resistor R3, the charge stored in Cf can be quickly released through the parallel resistor R3, thus ensuring that Usc returns to zero. The time constant T = R3Cf formed by resistor R3 and capacitor Cf determines the charge release speed in capacitor Cf. The smaller the time constant T, the faster the charging and discharging speed. Since 1 / Cf determines the amplification factor of the charge-sensitive amplifier circuit, the value of Cf should be small. However, the value of resistor R3 cannot be too small, otherwise the excessively fast discharge speed will affect the charging of capacitor Cf by the signal current. Therefore, resistor R3 cannot be too small or too large. In the current amplifier circuit, diodes D1 and D2 have exactly the same characteristics; the characteristics of NPN and PNP transistors must also be identical; resistors R6 and R7 have the same resistance value, as do resistors R8 and R9; resistors R6 and R7 are the base bias resistors for NPN and PNP transistors, respectively, and resistors R8 and R9 are the emitter resistors for NPN and PNP transistors, respectively; capacitors C3 and C4 are used for signal coupling, i.e., isolating DC noise while allowing pulse signals to pass through; resistors R6 and R7 are also required to maintain their positions. The function of R7 is to ensure that the DC bias voltage at the signal input terminal of the current amplifier circuit is 0 volts. The functions of resistors R8 and R9 as emitter resistors are, on the one hand, to ensure that the DC bias voltage at the signal output terminal of the current amplifier circuit is 0 volts, and on the other hand, to limit the current and prevent the transistor from thermally breaking down due to excessive current. Due to the introduction of R8 and R9, the output impedance of the entire current amplifier is not 0 ohms. In order to ensure a low impedance, the resistance values ​​of resistors R8 and R9 cannot be too large. It is only necessary to ensure that the collector current of the transistor is about 10mA. The function of diodes D1 and D2 is to eliminate waveform distortion caused by the transistor. The specific analysis is as follows: If diodes D1 and D2 were not present, the base potentials of the NPN and PNP transistors would be the same. When the output signal is 0 volts, there is no potential difference between the base and emitter, and no current is generated at the base. If the transistor is in the cutoff region and stops working, it will cause signal switching distortion. The transistor can only work when the base potential of the NPN transistor is about 0.6V higher than the emitter potential. Since a crystal diode has a forward voltage drop of about 0.6V, when diodes D1 and D2 are introduced into the circuit, this forward voltage drop of about 0.6V can be used as the compensation voltage for the transistor, thereby eliminating signal switching distortion. The positive and negative power supply circuits are designed to provide DC operating voltage to the entire amplifier circuit. The absolute values ​​of the positive and negative power supply voltages must be equal. A "Π"-type LC filter consisting of an inductor and two capacitors is designed at the ±VCC output terminal to eliminate AC noise from the ±VCC power supply from entering the signal transmission channel and improve the circuit signal-to-noise ratio.

2. The weak pulse signal amplification circuit according to claim 1, characterized in that: The operational amplifier IC1 is model AD8065.

3. The weak pulse signal amplification circuit according to claim 1, characterized in that: The operational amplifier IC2 is model AD8065.

Images