阅读说明：本技术 一种微弱脉冲信号放大电路 (Weak pulse signal amplifying circuit ) 是由 石苗 桂龙刚 毛向阳 吴永仁 管德赛 于 2019-12-19 设计创作，主要内容包括：本发明涉及一种微弱脉冲信号放大电路，包括探测器输出电路、一级电荷灵敏放大电路、二级负反馈放大电路、电流放大电路、正电源电路以及负电源电路六个单元电路。所述探测器输出电路、一级电荷灵敏放大电路、二级负反馈放大电路、电流放大电路这四个单元电路是通过耦合电容串联的，其中一级电荷灵敏放大电路、二级负反馈放大电路共同构成两级电压放大电路，整个电路的电压放大倍数是这两者各自的放大倍数的乘积。所述正负电源电路为整个电路提供工作电压。本发明电路既能实现电压放大，亦能实现电流放大，具有放大倍数高、信号频带宽、负载能力强、信噪比高、抗干扰能力强等优点。(The invention relates to a weak pulse signal amplification circuit which comprises six unit circuits, namely a detector output circuit, a primary charge sensitive amplification circuit, a secondary 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 amplifying circuit, the second-stage negative feedback amplifying circuit and the current amplifying circuit are connected in series through coupling capacitors, wherein the first-stage charge sensitive amplifying circuit and the second-stage negative feedback amplifying circuit jointly form a two-stage voltage amplifying circuit, and the voltage amplifying times of the whole circuit are the products of the respective amplifying times of the first-stage charge sensitive amplifying circuit and the second-stage negative feedback amplifying circuit. The positive and negative power supply circuit provides working voltage for the whole circuit. The circuit of the invention can realize voltage amplification and current amplification, and has the advantages of high amplification factor, wide signal frequency band, strong load capacity, high signal-to-noise ratio, strong anti-interference capacity and the like.)

1. A weak pulse signal amplifying circuit is characterized in that: the detector comprises a detector output circuit (1), a two-stage voltage amplifying circuit (2), a current amplifying circuit (3), a positive power supply circuit (4) and a negative power supply circuit (5), wherein the two-stage voltage amplifying circuit (2) is formed by connecting a first-stage charge sensitive amplifying circuit (2-1) and a second-stage negative feedback amplifying circuit (2-2) in series;

the detector output circuit (1) is electrically connected with a first-level charge sensitive amplifying circuit (2-1) in the two-level voltage amplifying circuit (2); the current amplifying circuit (3) is connected with a two-stage negative feedback amplifying circuit (2-2) in the two-stage voltage amplifying circuit (2); the detector output circuit (1), the primary charge sensitive amplifying circuit (2-1), the secondary negative feedback amplifying circuit (2-2) and the current amplifying circuit (3) are connected in series through capacitors; the positive power supply circuit and the negative power supply circuit simultaneously provide working voltage for the primary charge sensitive amplification circuit (2-1), the secondary negative feedback amplification circuit (2-2) and the current amplification circuit (3);

the detector output circuit (1) generates a pulse signal, the pulse signal enters a two-stage voltage amplifying circuit (2), the pulse signal is subjected to voltage amplification in the two-stage voltage amplifying circuit (2) through a first-stage charge sensitive amplifying circuit (2-1) and a second-stage negative feedback amplifying circuit (2-2) in sequence, the pulse signal subjected to voltage amplification enters a current amplifying circuit (3), and the pulse signal is output after current amplification.

2. The weak pulse signal amplifying circuit according to claim 1, wherein:

the detector output circuit comprises a detector, a high-voltage direct-current power supply (HV) output end, a resistor R1, a capacitor C1 and a capacitor C9; the ground end of the detector is grounded, the signal output end of the detector is simultaneously connected with one end of a resistor R1 and one end of a capacitor C1, the other end of a resistor R1 is simultaneously connected with the output end of a high-voltage direct-current power supply HV and one end of a capacitor C9, and the other end of a capacitor C9 is grounded;

the primary charge sensitive amplifying circuit comprises a resistor R2, an operational amplifier IC1, a capacitor Cf and a resistor R3; the other end of the capacitor C1, one end of the resistor R2, one end of the resistor R3 and one end of the capacitor Cf are simultaneously connected with a negative signal input end of the operational amplifier IC 1; the other end of the resistor R2 and the positive electrode signal input end of the operational amplifier IC1 are both grounded, and the other end of the resistor R3, the other end of the capacitor Cf and the signal output end of the operational amplifier IC1 are simultaneously connected with one end of the capacitor C2;

the two-stage negative feedback amplifying circuit comprises a capacitor C2, a resistor R4, a resistor R5 and an operational amplifier IC 2; the other end of the capacitor C2 is connected with one end of the resistor R4, the other end of the resistor R4 and one end of the resistor R5 are connected with a negative signal input end of the operational amplifier IC2, a positive signal input end of the operational amplifier IC2 is grounded, and the other end of the resistor R5 and a signal output end of the operational amplifier IC2 are simultaneously connected with one end of the capacitor C3;

the current amplification circuit comprises a capacitor C3, a diode D1, a diode D2, an NPN transistor, a PNP transistor, a resistor R6, a resistor R7, a resistor R8, a resistor R9 and a capacitor C4; the diode D1 and the diode D2 require the same characteristics, the NPN transistor and the PNP transistor require the same characteristics, the resistance values of the resistor R6 and the resistor R7 are equal, and the resistance values of the resistor R8 and the resistor R9 are also equal; the other end of the capacitor C3 is connected with the cathode of the diode D1 and the anode of the diode D2, the anode of the diode D1 is simultaneously connected with one end of a resistor R6 and the base level of a triode NPN, the emitter of the triode NPN is connected with one end of a resistor R8, the cathode of the diode D2 is simultaneously connected with one end of a resistor R7 and the base level of a triode PNP, the emitter of the triode PNP is connected with one end of a resistor R9, the other end of the resistor R8 and the other end of the resistor R9 are simultaneously connected with one end of a capacitor C4, and the other end of the capacitor C4;

the positive power supply circuit comprises a positive power supply output end + VCC, an inductor L1, a capacitor C5 and a capacitor C6; the inductor L1, the capacitor C5 and the capacitor C6 form a n-shaped LC filter; the + VCC output end is respectively connected with one end of a capacitor C5 and one end of an inductor L1, the other end of the inductor L1 is simultaneously connected with one end of a capacitor C6, the positive power input end of an operational amplifier IC1, the positive power input end of an operational amplifier IC2, the other end of a resistor R6 and a triode NPN collector, and the other end of the capacitor C5 and the other end of the capacitor C6 are both grounded;

the negative power supply circuit comprises a negative power supply output end-VCC, an inductor L2, a capacitor C7 and a capacitor C8; the inductor L2, the capacitor C7 and the capacitor C8 form an n-shaped LC filter, wherein a VCC output end is respectively connected with one end of the capacitor C7 and one end of the inductor L2, the other end of the inductor L2 is simultaneously connected with one end of the capacitor C8, a negative power input end of the operational amplifier IC1, a negative power input end of the operational amplifier IC2, the other end of the resistor R7 and a triode PNP collector, and the other end of the capacitor C7 and the other end of the capacitor C8 are grounded.

3. The weak pulse signal amplifying circuit according to claim 2, wherein: the model of the operational amplifier IC1 is AD 8065.

4. The weak pulse signal amplifying circuit according to claim 2, wherein: the model of the operational amplifier IC2 is AD 8065.

Technical Field

The invention relates to a weak pulse signal amplification circuit, and belongs to the technical field of nuclear radiation detection.

Background

The gas ionization detector is a widely-used detector in the field of nuclear radiation detection due to its high detection sensitivity. When the detector is irradiated with radiation, the radiation interacts with molecules in the gas to produce an ion pair consisting of an electron and a positive ion. In this case, if a dc high voltage is applied to the collector and the high voltage electrode constituting the detector, the electrons and positive ions are respectively pulled to the positive and negative electrodes by the electric field force and collected, and a pulse voltage signal is formed in the whole collection process. However, the voltage pulse signal output by the gas ionization detector is very weak, and the voltage amplitude is usually in the microvolt level (10)^-6V—10^-4V) and subsequent stages of the circuit for counting (counting circuit for short, which mainly performs the shaping and digital processing of the signal waveform) usually require signal amplitudes at least up to the magnitude of volts (10)⁰V). Obviously, such a weak voltage signal output by the detector must be voltage amplified before it can be used in the counting circuit.

At present, in the industry, a charge sensitive preamplifier is generally packaged at the signal output end of a gas ionization detector, and the charge sensitive preamplifier is used for amplifying a weak pulse signal. However, the simple charge sensitive preamplifier has two main drawbacks: firstly, the voltage amplification factor cannot be too large, and when the amplification factor is too large, the signal is affected by a limited gain-bandwidth product (GBP) generated by the operational amplifier, so that the bandwidth of the signal is reduced, which limits the application of the amplifying circuit to a certain extent; secondly, the load capacity is weak, the anti-interference is poor, and the long-distance transmission of signals cannot be realized.

Disclosure of Invention

The invention aims to provide a weak pulse signal amplifying circuit with high amplification factor, high signal-to-noise ratio, wide frequency band, strong interference resistance and strong load capacity.

The object of the invention is realized in this way, a weak pulse signal amplifying circuit is characterized in that: the detector comprises a detector output circuit, a two-stage voltage amplifying circuit, a current amplifying circuit, a positive power supply circuit and a negative power supply circuit, wherein the two-stage voltage amplifying circuit is formed by connecting a first-stage charge sensitive amplifying circuit and a second-stage negative feedback amplifying circuit in series;

the detector output circuit is electrically connected with a first-stage charge sensitive amplifying circuit in the two-stage voltage amplifying circuit; the current amplifying circuit is electrically connected with a secondary negative feedback amplifying circuit in the two-stage voltage amplifying circuit; the detector output circuit, the primary charge sensitive amplifying circuit, the secondary negative feedback amplifying circuit and the current amplifying circuit are connected in series through coupling capacitors; the positive power supply circuit and the negative power supply circuit simultaneously provide working voltage for the primary charge sensitive amplifying circuit, the secondary negative feedback amplifying circuit and the current amplifying circuit;

the detector output circuit generates a pulse signal, the pulse signal enters a two-stage voltage amplifying circuit, the pulse signal is subjected to voltage amplification in the two-stage voltage amplifying circuit through a first-stage charge sensitive amplifying circuit and a second-stage negative feedback amplifying circuit in sequence, the pulse signal subjected to voltage amplification enters a current amplifying circuit, and the pulse signal is output after current amplification.

The detector output circuit comprises a detector, a high-voltage direct-current power supply (HV) output end, a resistor R1, a capacitor C1 and a capacitor C9; the ground end of the detector is grounded, the signal output end of the detector is simultaneously connected with one end of a resistor R1 and one end of a capacitor C1, the other end of a resistor R1 is simultaneously connected with the output end of a high-voltage direct-current power supply HV and one end of a capacitor C9, and the other end of a capacitor C9 is grounded;

the primary charge sensitive amplifying circuit comprises a resistor R2, an operational amplifier IC1, a capacitor Cf and a resistor R3; the other end of the capacitor C1, one end of the resistor R2, one end of the resistor R3 and one end of the capacitor Cf are simultaneously connected with a negative signal input end of the operational amplifier IC 1; the other end of the resistor R2 and the positive electrode signal input end of the operational amplifier IC1 are both grounded, and the other end of the resistor R3, the other end of the capacitor Cf and the signal output end of the operational amplifier IC1 are simultaneously connected with one end of the capacitor C2;

the two-stage negative feedback amplifying circuit comprises a capacitor C2, a resistor R4, a resistor R5 and an operational amplifier IC 2; the other end of the capacitor C2 is connected with one end of the resistor R4, the other end of the resistor R4 and one end of the resistor R5 are connected with a negative signal input end of the operational amplifier IC2, a positive signal input end of the operational amplifier IC2 is grounded, and the other end of the resistor R5 and a signal output end of the operational amplifier IC2 are simultaneously connected with one end of the capacitor C3;

the current amplification circuit comprises a capacitor C3, a diode D1, a diode D2, an NPN transistor, a PNP transistor, a resistor R6, a resistor R7, a resistor R8, a resistor R9 and a capacitor C4; the diode D1 and the diode D2 require the same characteristics, the NPN transistor and the PNP transistor require the same characteristics, the resistance values of the resistor R6 and the resistor R7 are equal, and the resistance values of the resistor R8 and the resistor R9 are also equal; the other end of the capacitor C3 is connected with the cathode of the diode D1 and the anode of the diode D2, the anode of the diode D1 is simultaneously connected with one end of a resistor R6 and the base level of a triode NPN, the emitter of the triode NPN is connected with one end of a resistor R8, the cathode of the diode D2 is simultaneously connected with one end of a resistor R7 and the base level of a triode PNP, the emitter of the triode PNP is connected with one end of a resistor R9, the other end of the resistor R8 and the other end of the resistor R9 are simultaneously connected with one end of a capacitor C4, and the other end of the capacitor C4;

the positive power supply circuit comprises a positive power supply output end + VCC, an inductor L1, a capacitor C5 and a capacitor C6; the inductor L1, the capacitor C5 and the capacitor C6 form a n-shaped LC filter; the + VCC output end is respectively connected with one end of a capacitor C5 and one end of an inductor L1, the other end of the inductor L1 is simultaneously connected with one end of a capacitor C6, the positive power input end of an operational amplifier IC1, the positive power input end of an operational amplifier IC2, the other end of a resistor R6 and a triode NPN collector, and the other end of the capacitor C5 and the other end of the capacitor C6 are both grounded;

the negative power supply circuit comprises a negative power supply output end-VCC, an inductor L2, a capacitor C7 and a capacitor C8; the inductor L2, the capacitor C7 and the capacitor C8 form an n-shaped LC filter, wherein a VCC output end is respectively connected with one end of the capacitor C7 and one end of the inductor L2, the other end of the inductor L2 is simultaneously connected with one end of the capacitor C8, a negative power input end of the operational amplifier IC1, a negative power input end of the operational amplifier IC2, the other end of the resistor R7 and a triode PNP collector, and the other end of the capacitor C7 and the other end of the capacitor C8 are grounded.

The model of the operational amplifier IC1 is AD 8065.

The model of the operational amplifier IC2 is AD 8065.

The invention has the beneficial effects that:

firstly, the amplification of the circuit to the voltage signal with extremely weak amplitude is realized by connecting a first-stage charge sensitive amplification circuit and a second-stage negative feedback amplification circuit in series, the amplification factor is the product of the amplification factors of the two amplification modules, so that the respective amplification factors of the first-stage charge sensitive amplification circuit and the second-stage negative feedback amplification circuit can be not too high, further, the whole circuit can not be influenced by the finite Gain Bandwidth Product (GBP) of an operational amplifier and the Open Loop Gain (OLG) of the whole circuit, and the circuit can ensure that the input end of the operational amplifier obtains high input impedance while obtaining low level offset. Therefore, the circuit has the advantages of high amplification factor and wide frequency band.

Secondly, the current amplification circuit in the circuit is ingenious in design, not only can realize current amplification, ensure that output signals are anti-interference and strong in load capacity, further realize remote transmission of signals, but also cannot cause waveform distortion caused by intercepting of negative half-axis voltage waveforms.

Thirdly, the circuit not only designs a unit for filtering noise waves for the output circuit of the detector, the primary charge sensitive amplifying circuit and the power circuit part, but also adds coupling capacitors among amplifying modules in the signal transmission process, and the coupling capacitors can play an isolation role in direct current noise mixed in pulse signals. By these measures, the noise is effectively reduced, and the signal-to-noise ratio (signal voltage amplitude/noise voltage amplitude) of the whole circuit is improved.

In summary, the weak pulse signal amplifying circuit provided by the invention comprises six unit circuits, namely a detector output circuit, a primary charge sensitive amplifying circuit, a secondary negative feedback amplifying circuit, a current amplifying circuit, a positive power supply circuit and a negative power supply circuit. The detector output circuit, the first-stage charge sensitive amplifying circuit, the second-stage negative feedback amplifying circuit and the current amplifying circuit are connected in series through coupling capacitors, wherein the first-stage charge sensitive amplifying circuit and the second-stage negative feedback amplifying circuit jointly form a two-stage voltage amplifying circuit, and the voltage amplifying times of the whole circuit are the products of the respective amplifying times of the first-stage charge sensitive amplifying circuit and the second-stage negative feedback amplifying circuit. The positive and negative power supply circuit provides working voltage for the whole circuit. The circuit of the invention can realize voltage amplification and current amplification, and has the advantages of high amplification factor, wide signal frequency band, strong load capacity, high signal-to-noise ratio, strong anti-interference capability and the like.

Drawings

FIG. 1 is a schematic diagram of the circuit of the present invention;

FIG. 2 is a block diagram of a circuit configuration;

in the figure, a detector output circuit 1, a two-stage voltage amplifying circuit 2, a one-stage charge sensitive amplifying circuit 2-1, a two-stage negative feedback amplifying circuit 2-2, a current amplifying circuit 3, a positive power supply circuit 4 and a negative power supply circuit 5.

Detailed Description

The structure of the circuit of the present invention will be described in general with reference to the accompanying drawing 1 of the specification:

a weak pulse signal amplifying circuit comprises a detector output circuit 1, a two-stage voltage amplifying circuit 2, a current amplifying circuit 3, a positive power supply circuit 4 and a negative power supply circuit 5, wherein the two-stage voltage amplifying circuit 2 is formed by connecting a first-stage charge sensitive amplifying circuit 2-1 and a second-stage negative feedback amplifying circuit 2-2 in series; the detector output circuit 1 is connected with a first-stage charge sensitive amplifying circuit 2-1 in the two-stage voltage amplifying circuit 2; the current amplifying circuit 3 is connected with a second-stage negative feedback amplifying circuit 2-2 in the two-stage voltage amplifying circuit 2; the detector output circuit 1, the primary charge sensitive amplifying circuit 2-1, the secondary negative feedback amplifying circuit 2-2 and the current amplifying circuit 3 are connected in series through capacitors; the positive power supply circuit and the negative power supply circuit simultaneously provide working voltage for the first-stage charge sensitive amplifying circuit 2-1, the second-stage negative feedback amplifying circuit 2-2 and the current amplifying circuit 3.

The detector output circuit 1 generates a pulse signal, the pulse signal enters a two-stage voltage amplifying circuit 2, the pulse signal is subjected to voltage amplification in the two-stage voltage amplifying circuit 2 through a first-stage charge sensitive amplifying circuit 2-1 and a second-stage negative feedback amplifying circuit 2-2 in sequence, the pulse signal subjected to voltage amplification enters a current amplifying circuit 3, and the pulse signal is output after current amplification.

Namely:

the first step is as follows: the pulse signal is generated by the detector output circuit 1.

The second step is that: the pulse signal enters a two-stage voltage amplifying circuit 2 for voltage amplification, wherein the two-stage voltage amplifying circuit 2 is formed by connecting a first-stage charge sensitive amplifying circuit 2-1 and a second-stage negative feedback amplifying circuit 2-2 in series, and the total voltage amplification factor is the product of the respective amplification factors of the first-stage charge sensitive amplifying circuit 2-1 and the second-stage negative feedback amplifying circuit 2-2.

Thirdly, the pulse signal amplified by the voltage enters a current amplifying circuit 3, and the signal is output after the current amplification.

In the whole process, the positive power supply circuit and the negative power supply circuit are required to simultaneously provide working voltage for the secondary voltage amplifying circuit and the current amplifying circuit.

The principle, function and attention of each unit circuit in the circuit of the present invention will be described in detail with reference to the accompanying fig. 2:

a weak pulse signal amplifying circuit is characterized in that: the detector comprises a detector output circuit, a first-stage charge sensitive amplifying circuit, a second-stage negative feedback amplifying circuit, a current amplifying circuit, a positive power supply circuit and a negative power supply circuit, and can realize voltage two-stage amplification and current amplification.

The detector output circuit comprises a detector, a high-voltage direct-current power supply HV output end, a resistor R1, a capacitor C1 and a capacitor C9. Wherein: the ground end of the detector is grounded, the signal output end is simultaneously connected with one end of a resistor R1 and one end of a capacitor C1, the other end of a resistor R1 is simultaneously connected with the output end of a high-voltage direct-current power supply HV and one end of a capacitor C9, and the other end of a capacitor C9 is grounded.

The first-stage charge sensitive amplifying circuit comprises a resistor R2 and an operational amplifier IC1 (model is AD8065, and amplification factor is A)₀) A capacitor Cf and a resistor R3. Wherein: the other end of the capacitor C1, one end of the resistor R2, one end of the resistor R3 and one end of the capacitor Cf are connected with the negative signal input end of the operational amplifier IC 1. The other end of the resistor R2 and an operational amplifierThe positive signal input terminal of the IC1 is grounded, and the other terminal of the resistor R3, the other terminal of the capacitor Cf, and the signal output terminal of the operational amplifier IC1 are connected to one terminal of the capacitor C2.

The second-stage negative feedback amplifying circuit comprises a capacitor C2, a resistor R4, a resistor R5 and an operational amplifier IC2 (model number is AD8065, and amplification factor is A₀). Wherein: the other end of the capacitor C2 is connected with one end of the resistor R4, the other end of the resistor R4 and one end of the resistor R5 are connected with a negative signal input end of the operational amplifier IC2, a positive signal input end of the operational amplifier IC2 is grounded, and the other end of the resistor R5 and a signal output end of the operational amplifier IC2 are simultaneously connected with one end of the capacitor C3.

The current amplifying circuit comprises a capacitor C3, a diode D1, a diode D2, an NPN transistor, a PNP transistor, a resistor R6, a resistor R7, a resistor R8, a resistor R9 and a capacitor C4. The diode D1 and the diode D2 require the same characteristics, the NPN transistor and the PNP transistor require the same characteristics, the resistance values of the resistor R6 and the resistor R7 are equal, and the resistance values of the resistor R8 and the resistor R9 are also equal. The other end of the capacitor C3 is connected to the cathode of the diode D1 and the anode of the diode D2, the anode of the diode D1 is connected to one end of the resistor R6 and the base of the transistor NPN, the emitter of the transistor NPN is connected to one end of the resistor R8, the cathode of the diode D2 is connected to one end of the resistor R7 and the base of the transistor PNP, the emitter of the transistor PNP is connected to one end of the resistor R9, the other end of the resistor R8 and the other end of the resistor R9 are connected to one end of the capacitor C4, and the other end of the capacitor C4 outputs a signal.

The positive power supply circuit comprises a positive power supply output end + VCC, an inductor L1, a capacitor C5 and a capacitor C6. The inductor L1, the capacitor C5 and the capacitor C6 form a pi-type LC filter, wherein: the + VCC output end is respectively connected with one end of a capacitor C5 and one end of an inductor L1, the other end of the inductor L1 is simultaneously connected with one end of a capacitor C6, the positive power input end of an operational amplifier IC1, the positive power input end of an operational amplifier IC2, the other end of a resistor R6 and a triode NPN collector, and the other end of the capacitor C5 and the other end of the capacitor C6 are both grounded.

The negative power supply circuit comprises a negative power supply output end VCC, an inductor L2, a capacitor C7 and a capacitor C8. The inductor L2, the capacitor C7 and the capacitor C8 form a pi-type LC filter, wherein: the VCC output end is connected to one end of a capacitor C7 and one end of an inductor L2, the other end of the inductor L2 is connected to one end of a capacitor C8, a negative power input end of an operational amplifier IC1, a negative power input end of an operational amplifier IC2, the other end of a resistor R7 and a triode PNP collector, and the other end of the capacitor C7 and the other end of the capacitor C8 are both grounded.

According to the description and the attached figure 2, in the detector output circuit, the working voltage of the detector is provided by a high-voltage direct-current power supply HV, and for the pulse signal generated by the detector, because the resistance of a resistor R1 is large, and the resistance of a capacitor C1 is small, the pulse signal can be approximately considered to enter the following one-stage charge sensitive amplifying circuit only through a capacitor C1. The capacitor C1 acts as a signal coupling, i.e. isolates the dc voltage HV, allowing the pulse signal to pass. The resistor R1 and the capacitor C9 form an RC low-pass filter, so that low-frequency noise generated by the high-voltage direct-current power supply module can be prevented from entering a first-stage charge sensitive amplifying circuit.

According to the specification and the attached figure 2, in the one-stage charge sensitive amplifying circuit, a capacitor C1 and a resistor R2 form a CR high-pass filter, and pulse signals with the cut-off frequency higher than the filter can be allowed to pass through and noise with the cut-off frequency lower than the filter is prevented from entering the amplifier by selecting a proper capacitor C1 and a resistor R2. The capacitance Cf represents a feedback capacitance, the value of which directly determines the amplification factor of the whole charge-sensitive amplification circuit, and the detailed derivation process is as follows:

suppose the amplification of the operational amplifier IC1 is A₀The total capacitance at the input is C, the voltage signal at the input of op-amp IC1 is Usr, and the average charge formed by the detector producing a signal is Q.

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

C＝(1+A₀)Cf (1)

The voltage signal Usr formed at the input of the operational amplifier IC1 is

Because of the amplification factor (A) of the operational amplifier IC1₀) Far greater than 1, then

Since the operational amplifier IC1 is in negative feedback connection, the output voltage signal U of the amplifier_scIs composed of

As shown in the formula (4), the voltage pulse signal Usc output by the amplifier is proportional to the charge Q generated by the detector and is proportional to the amplification factor A of the operational amplifier₀Is irrelevant. Since the unit charge generated by the detector can output a voltage with the amplitude value of Usc-1/Cf through the amplifier, the voltage is called a charge sensitive voltage, the amplifier is called a charge sensitive amplifier, and the voltage amplification factor of the amplifier is 1/Cf, so that the amplification factor of the charge sensitive amplifier circuit can be changed by changing the value of Cf.

The resistor R3 is used to drain the charge stored on the capacitor Cf: when a pulse signal current charges Cf, the charge in Cf must be released quickly to continue charging the next signal current, otherwise the following two consequences are caused: firstly, the capacitor is charged continuously, if the capacitor does not release the charge, Cf is broken down, and secondly, different pulse signals are accumulated to cause signal accumulation. Due to the presence of resistor R3, the charge stored in Cf can be quickly discharged through parallel resistor R3, ensuring that Usc is zeroed. The time constant T of the resistor R3 and the capacitor Cf, R3Cf, determines the charge discharging rate of the capacitor Cf, and the smaller the time constant T, the faster the charge and discharge rate. Since 1/Cf determines the amplification factor of the charge-sensitive amplifier circuit, the Cf value should be selected to be small, but the value of the resistor R3 cannot be too small, otherwise, the too fast discharge speed affects the charging of the capacitor Cf by the signal current, and therefore the resistor R3 cannot be too small or too large.

If only one-stage charge sensitive amplifying circuit is adopted, when the voltage amplification factor is too large, the pulse signal is influenced by the finite Gain Bandwidth Product (GBP) of the operational amplifier, so that the pulse width of the signal is reduced, and the amplification factor-1/Cf of the charge sensitive amplifying circuit cannot be too large. In order to solve the problem, a two-stage negative feedback amplifying circuit is connected in series behind the first-stage charge sensitive amplification.

According to the figure 2 in the specification, in the two-stage negative feedback amplifying circuit, the amplification factor is determined by a resistor R4 and a resistor R5, and the amplification factor is-R5/R4. The resistor C2 functions to couple signals, i.e., isolate dc noise signals, while allowing pulsed signals to pass through.

According to the above, after the pulse signal is amplified by two stages of voltages, the total voltage amplification factor is (-1/Cf) — R5/R4). In order to ensure that the pulse voltage signal has enough anti-interference capability and load capability to realize the long-distance transmission of the pulse signal, the invention is connected with a current amplifying circuit in series behind the secondary negative feedback circuit.

Generally, the current amplification can be replaced by an emitter follower mainly composed of a triode NPN, which has the advantages of high input impedance, low output impedance, strong load carrying capacity and the like. However, since the emitter of the amplifier has a load resistor, when the output current is large, that is, the impedance is low, the negative half-axis of the output waveform is cut off, and the full output maximum voltage cannot be obtained, thereby causing signal distortion. To improve the performance and improve the defect, the emitter load resistor is usually replaced by a PNP triode in engineering to form a conventional push-pull emitter follower.

However, the invention makes the following optimization improvements on the conventional push-pull emitter follower:

according to the description of fig. 2, in the current amplifying circuit, the diode D1 and the diode D2 have the same characteristics. The characteristics of the triode NPN and the triode PNP are required to be consistent, the resistance values of the resistor R6 and the resistor R7 are the same, and the resistance values of the resistor R8 and the resistor R9 are also the same. The resistor R6 and the resistor R7 are base bias resistors of the triode NPN and the triode PNP respectively, and the resistor R8 and the resistor R9 are emitter resistors of the triode NPN and the triode PNP respectively. The capacitor C3 and the capacitor C4 are used for signal coupling, i.e., isolating direct current noise, and allowing pulse signals to pass through. The resistor R6 and the resistor R7 are used for ensuring that the direct current bias voltage of the signal input end of the current amplifying circuit is 0 volt. The resistor R8 and the resistor R9 are used as emitter resistors, so that the direct-current bias voltage of the signal output end of the current amplification circuit is ensured to be 0 volt on one hand, and the current is limited on the other hand, and thermal breakdown of the triode caused by overlarge current is avoided. Due to the introduction of R8 and R9, the output impedance of the whole current amplifier is not 0 ohm, and in order to ensure that the impedance is low, the resistance values of the resistor R8 and the resistor R9 cannot be too large, only the collector current of the triode needs to be ensured to be about 10 mA.

The diode D1 and the diode D2 function to eliminate waveform distortion caused by the triode. The specific analysis is as follows: without the two diodes D1 and D2, the base potentials of the NPN and PNP are the same. When the output signal is 0V, no potential difference exists between the base electrode and the emitter electrode, the base electrode cannot generate current, and at the moment, if the triode is positioned in a cut-off region and stops working, the switching distortion of the signal can be caused. The triode can only operate when the base potential of the NPN is about 0.6V higher than the emitter potential. Since the transistor diode has a forward voltage drop of about 0.6V, when the diode D1 and the diode D2 are introduced into the circuit, the forward voltage drop of about 0.6V is just applicable to the compensation voltage of the triode, thereby eliminating signal switching distortion.

According to the attached figure 2 of the specification, the positive power circuit and the negative power circuit have the function that in order to provide direct-current working voltage for the whole amplifying circuit, the absolute value requirements of the voltage of the positive power supply and the voltage of the negative power supply must be equal, and a n-shaped LC filter formed by an inductor and two capacitors is designed at the output end of +/-VCC so as to eliminate alternating-current noise brought by the +/-VCC power supply from entering a signal transmission channel and improve the signal-to-noise ratio of the circuit.