Debugging Methods of Discrete Input Stage Transimpedance Amplifier

Abstract

The present invention relates to the field of electronic information technology, and in particular to a debugging method for a discrete input-stage transimpedance amplifier, which first completes the construction of a cutoff voltage test circuit and a drain-source saturation current test circuit to obtain the calculation parameters of a field effect tube; then completes the construction of a source resistance matching circuit, and obtains the corresponding relationship between the source voltage and the source resistance according to the calculation parameters; substitutes the set theoretical source voltage into the corresponding relationship to obtain the theoretical source resistance, and then connects the theoretical source resistance to the source resistance matching circuit to measure the actual source voltage, and fine-tunes the theoretical source resistance according to the actual source voltage and the theoretical source resistance to obtain the real source resistance. This method solves the complex and repeated operations of source resistance trial and error, and improves the debugging efficiency.

Description

Technical Field

[0001] The invention belongs to the field of electronic information technology, and in particular relates to a debugging method for a discrete input-stage transimpedance amplifier. Background Art

[0002] Transimpedance amplifier is an important front-end amplifier circuit in the field of weak signal detection, which is used to realize weak current-voltage conversion. Since field effect tubes have high input impedance, they are often used as input stages to form discrete transimpedance amplifier circuits. The discrete transimpedance amplifier circuit using field effect tubes as input stages has lower background noise because the equivalent input current of the operational amplifier is short-circuited by the drain-source resistance of the field effect tube. However, the introduction of field effect tubes has brought new problems. The parameters of field effect tubes are highly discrete, and there are errors between the relevant parameters and the reference values ​​in the technical manual. The given reference values ​​cannot be substituted into the circuit parameters for analysis. At the same time, it is necessary to select a source resistor that matches the parameters of the field effect tube so that the field effect tube works in the constant current region. Only in this way can the drain current be controlled by the gate-source voltage to achieve matching of the discrete transimpedance amplifier circuit parameters.

[0003] Currently, the selection of source resistance mostly adopts the "trial and error method", which is to make the gate-source voltage of the field effect tube between 0 and the cut-off voltage of the field effect tube by constantly trying resistors of different resistance values. However, this method is difficult and complicated to operate, has low implementation efficiency, does not protect the circuit, and is easy to exceed the threshold, break down the field effect tube, and damage the circuit. Summary of the invention

[0004] In view of this, the present invention aims to provide a debugging method for a discrete input stage transimpedance amplifier, which accurately determines the parameters of the field effect transistor used in the discrete transimpedance amplifier through a cutoff voltage test circuit and a drain-source saturation current test circuit, and then adopts a source resistance matching method, combined with a source resistance matching circuit, to accurately match the source resistance according to the required source voltage, thereby achieving matching of the circuit parameters of the discrete transimpedance amplifier.

[0005] To achieve the above object, the technical solution created by the present invention is implemented as follows:

[0006] A debugging method for a discrete input-stage transimpedance amplifier specifically comprises the following steps:

[0007] S1: Build a cut-off voltage test circuit and obtain the cut-off voltage U of the field effect tube GSoff ;

[0008] S2: Build a drain-source saturation current test circuit and obtain the drain-source saturation current I of the field effect tube DSS ;

[0009] S3: Build a source resistance matching circuit to obtain the source voltage U connected to the field effect tube S, a first corresponding relationship among the source resistance R and the supply voltage V;

[0010] S4: through cut-off voltage U GSoff , drain-source saturation current I DSS And the first corresponding relationship to obtain the source voltage U S A second corresponding relationship with the source resistance R;

[0011] S5: Set the theoretical source voltage U S0 Substituting into the second corresponding relationship, the theoretical source resistance R0 is obtained, and the theoretical source resistance R0 is connected to the source resistance matching circuit to measure the actual source voltage U S ′;

[0012] S6: Fine-tune the theoretical source resistance R0 until the actual source voltage U′ S With the theoretical source voltage U S0 When the difference is within ±5% or ±1%, the current source resistance is the true source resistance R′.

[0013] Furthermore, in step S1, the cut-off voltage test circuit includes a field effect transistor and an ammeter; wherein the gate voltage U G Connect to the gate of the field effect tube, the source voltage U S Connect to the source and drain voltage of the field effect tube U D Connect to the drain of the field effect tube, and connect the ammeter to the drain to measure the drain current I D ; Change the gate voltage U G , when the drain current I D When the voltage between the gate and the source approaches 0, it is the cut-off voltage U GSoff .

[0014] Further, in step S2, the gate and source are grounded, the ammeter is connected to the drain, and the drain voltage U D Connect to the drain to get the drain-source saturation current test circuit; the ammeter measures the drain current I D The drain-source saturation current I DSS .

[0015] Furthermore, in step S3, the source is connected to the source resistor R and connected to the source voltage U S , the supply voltage V is applied to the drain, and the ammeter is connected to the drain to measure the drain current I D , and the source resistance matching circuit is obtained; at this time, the first corresponding relationship is:

[0016] U S -(-V)=I D ×R.

[0017] Further, in step S4, according to the cut-off voltage UGSoff and the drain-source saturation current I DSS , drain current I D It is expressed as:

[0018]

[0019] Among them, U GS =U G -U S Represents the voltage between the gate and the source; due to U G =0,U GS =-U S , at this time the drain current I D It is expressed as:

[0020]

[0021] According to the first corresponding relationship and the drain current I D Get the source voltage and solve the equation:

[0022]

[0023] Solve the equation for the source voltage to get the source voltage U S for:

[0024]

[0025] Since the cut-off voltage U GSoff Less than 0, source voltage U S satisfy:

[0026] 0≤U S ≤-U Gsoff ;

[0027] At this time, the source voltage U S Simplify the second corresponding relationship, namely:

[0028]

[0029] Compared with the prior art, the invention can achieve the following beneficial effects:

[0030] The debugging method of the discrete input-stage transimpedance amplifier created by the present invention adopts a cutoff voltage test circuit and a drain-source saturation current test circuit to accurately obtain the parameters of the field effect tube, thereby avoiding errors caused by inaccurate reference values. Through the source resistance matching circuit, the source resistance can be accurately matched according to the source voltage. This method solves the complex and repeated operations of source resistance matching, improves the debugging efficiency, and can effectively solve the problem of field effect tube breakdown and circuit damage caused by improper source resistance selection. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0032] Figure 1 A flowchart of a debugging method for a discrete input-stage transimpedance amplifier according to an embodiment of the present invention;

[0033] Figure 2 A schematic diagram of the circuit structure of a cut-off voltage test circuit according to an embodiment of the present invention;

[0034] Figure 3 A schematic diagram of the circuit structure of a drain-source saturation current test circuit according to an embodiment of the present invention;

[0035] Figure 4 A schematic diagram of the circuit structure of a source resistance matching circuit according to an embodiment of the present invention;

[0036] Figure 5 A function curve diagram of the second corresponding relationship described in the embodiment of the present invention;

[0037] Figure 6 The simulation structure curve diagram described in the embodiment of the present invention is created.

[0038] Description of reference numerals:

[0039] U D , drain voltage; A, ammeter; I D , drain current; D, drain; G, gate; U G , gate voltage; S, source; U S , source voltage; V, supply voltage; R, source resistance. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the invention more clear, the invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described here are only used to explain the invention and do not constitute a limitation of the invention.

[0041] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0042] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0043] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0044] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0045] like Figures 1 to 4 As shown, the debugging method of the discrete input stage transimpedance amplifier described in the embodiment of the present invention specifically includes the following steps:

[0046] S1: Build a cut-off voltage test circuit and obtain the cut-off voltage U of the field effect tube GSoff .

[0047] Among them, the cut-off voltage test circuit is as follows Figure 2 As shown, it includes a field effect tube and an ammeter A; wherein the gate voltage U G Connect to the gate G of the field effect tube, the source voltage U S Connect to the source S of the field effect tube, the drain voltage U D Connect to the drain D of the field effect tube, and connect the ammeter A to the drain D to measure the drain current I D . Change the gate voltage U G , when the drain current I D When it approaches 0, the voltage between the gate G and the source S is the cut-off voltage U. GSoff .

[0048] S2: Build a drain-source saturation current test circuit and obtain the drain-source saturation current I of the field effect tube DSS .

[0049] Among them, the drain-source saturation current test circuit is as follows Figure 3 As shown, the gate G and source S are grounded, the ammeter A is connected to the drain D, and the drain voltage U D Connect the drain D to get the drain-source saturation current test circuit. At this time, the ammeter A measures the drain current I D The drain-source saturation current I DSS .

[0050] S3: Build a source resistance matching circuit to obtain the source voltage U connected to the field effect tube S , a first corresponding relationship between the source resistance R and the supply voltage V.

[0051] Among them, the source S is connected to the source resistor R and connected to the source voltage U S , the supply voltage V is applied to the drain D, and the ammeter A is connected to the drain D to measure the drain current I D , and the source resistance matching circuit is obtained. At this time, the first corresponding relationship is:

[0052] U S -(-V)=I D ×R.

[0053] S4: through cut-off voltage U GSoff , drain-source saturation current I DSS And the first corresponding relationship to obtain the source voltage U S The second corresponding relationship with the source resistance R.

[0054] When a field effect tube is used as the input stage of a transimpedance amplifier circuit, the field effect tube needs to work in the constant current region. At this time, the voltage U between the gate G and the source S is GS =U G -U S <0. In the circuit, due to the gate voltage U G =0, so the source voltage U S >0. Drain current I D Flows through the source resistor R. If the source resistor R increases, the voltage divided by the source resistor R will increase, and the source voltage U S will also increase, so that the voltage U between the gate G and the source S GS The decrease will cause the drain current I D Reduce, drain current I D After the source resistance R is reduced, the voltage division will decrease again, and the source voltage U S Therefore, in the circuit, the source resistance R and the source voltage U SIt has become a changing balance, and the relationship between the two can be modeled and analyzed using a quadratic equation.

[0055] According to the cut-off voltage U GSoff and the drain-source saturation current I DSS , drain current I D It is expressed as:

[0056]

[0057] According to the virtual short and virtual break principle of field effect tube, U G =0,U GS =-U S , at this time the drain current I D It is expressed as:

[0058]

[0059] According to the first corresponding relationship and the drain current I D Get the source voltage and solve the equation:

[0060]

[0061] Since there is a discriminant Δ in the source voltage solution equation:

[0062]

[0063] Since the cut-off voltage U GSoff Less than 0, so the discriminant Δ is always greater than 0, and the source voltage U can be solved S for:

[0064]

[0065] Since the source resistance R in the circuit cannot be too large, an excessively large source resistance R will cause the voltage U between the gate G and the source S to GS Less than cut-off voltage U GSoff , so that the field effect tube works in the cut-off region, so the source voltage U S satisfy:

[0066] 0≤U S ≤-U GSoff ;

[0067] At this time, the source voltage U S Simplify the second corresponding relationship, namely:

[0068]

[0069] S5: Set the theoretical source voltage U S0Substituting into the second corresponding relationship, the theoretical source resistance R0 is obtained, and the theoretical source resistance R0 is connected to the source resistance matching circuit to measure the actual source voltage U S ′.

[0070] S6: Fine-tune the theoretical source resistance R0 until the actual source voltage U′ S With the theoretical source voltage U S0 When the difference is within ±5% or ±1%, the current source resistance is the true source resistance R′.

[0071] In order to verify the effectiveness of the debugging method for the discrete input stage transimpedance amplifier described in the embodiment of the invention, the operations described in the specific embodiment were performed. Specific embodiment:

[0073] According to the technical manual, the experiment uses the drain-source saturation current I of the field effect tube DSS The current is 15 mA, but during the experiment, it was found that its discreteness is extremely large and its performance is far from the typical value in the technical manual. Therefore, the correctness of the result was verified in the simulation software.

[0074] According to step S1, a cut-off voltage test circuit is built to set the voltage U between the drain D and the source S of the field effect tube. DS is 10V. Change the gate voltage U G , when the drain current I D When the cut-off voltage U between the gate G and the source S is measured, it tends to 0. GSoff About -2.75V.

[0075] According to step S2, a drain-source saturation current test circuit is constructed to maintain the voltage U between the drain D and the source S. DS Still at 10V, the gate G and source S are both grounded so that the voltage U between the two electrodes GS is 0, at this time the drain-source saturation current I DSS About 20.4mA.

[0076] According to step S3, a source resistance matching circuit is constructed and the supply voltage V is set to 10V.

[0077] According to step S4, the source voltage U is obtained S The second corresponding relationship with the source resistance R, the function curve of the second corresponding relationship is as follows Figure 6 shown.

[0078] According to step S5, in order to avoid the field effect tube working in the cut-off region due to waveform fluctuation, the theoretical source voltage U is set S0 is 1V, and is substituted into the second corresponding relationship to calculate that the theoretical source resistance R0 is about 1.335kΩ.S0 The theoretical source resistance R0 is connected to the source resistance matching circuit, and the actual source voltage U is measured. S 'like Figure 6 As shown, it is 1.0175V.

[0079] According to step S6, the actual source voltage U′ s =1.0175V and theoretical source voltage U S0 =1V is within ±5% or ±1%, indicating that the actual source resistance R' can be obtained without adjusting the theoretical source resistance R0, which means that the debugging method of the discrete input stage transimpedance amplifier described in the embodiment of the invention is practical and effective. When the actual circuit is built and operated, the theoretical source resistance R0 can be used to adjust and determine the actual source voltage U' S With the theoretical source voltage U S0 Whether the difference is within ±5% or ±1%, the actual source resistance R′ is obtained.

[0080] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the disclosure of the present invention can be performed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and this document does not limit this.

[0081] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for debugging a discrete input-stage transimpedance amplifier, characterized in that: The specific steps include: S1: Build a cut-off voltage test circuit and obtain the cut-off voltage U of the field effect tube GSoff ; S2: Build a drain-source saturation current test circuit and obtain the drain-source saturation current I of the field effect transistor DSS ; S3: Build a source resistance matching circuit to obtain the source voltage U connected to the field effect tube S , a first corresponding relationship among the source resistance R and the supply voltage V; S4: through the cut-off voltage U GSoff , the drain-source saturation current I DSS The source voltage U is obtained by the first corresponding relationship S A second corresponding relationship with the source resistance R; S5: Set the theoretical source voltage U S0 Substituting the theoretical source resistance R0 into the second corresponding relationship, and connecting the theoretical source resistance R0 to the source resistance matching circuit to measure the actual source voltage U S ′; S6: fine-tune the theoretical source resistance R0 until the actual source voltage U′ S With the theoretical source voltage U S0 When the difference is within ±5% or ±1%, the current source resistance is the true source resistance R′.

2. The debugging method of discrete input stage transimpedance amplifier according to claim 1, characterized in that: In step S1, the cut-off voltage test circuit includes a field effect transistor and an ammeter; wherein the gate voltage U G connected to the gate of the field effect tube, the source voltage U S The source and drain voltage U of the field effect tube are connected. D The drain of the field effect tube is connected, and the ammeter is connected to the drain to measure the drain current I D ; Change the gate voltage U G , when the drain current I D When the voltage between the gate and the source is close to 0, the cut-off voltage U GSoff .

3. The debugging method of discrete input stage transimpedance amplifier according to claim 2, characterized in that: In step S2, the gate and the source are grounded, the ammeter is connected to the drain, and the drain voltage U D Connecting to the drain electrode, obtaining the drain-source saturation current test circuit; the ammeter measures the drain current I D That is, the drain-source saturation current I DSS .

4. The debugging method of discrete input stage transimpedance amplifier according to claim 3, characterized in that: In step S3, the source is connected to the source resistor R and connected to the source voltage U S , the supply voltage V is applied to the drain, the ammeter is connected to the drain to measure the drain current I D , the source resistance matching circuit is obtained; at this time, the first corresponding relationship is: U S -(-V)=I D ×R。 5. The debugging method of discrete input stage transimpedance amplifier according to claim 4, characterized in that: In step S4, according to the cut-off voltage U GSoff and the drain-source saturation current I DSS , the drain current I D It is expressed as: Among them, U GS =U G -U S represents the voltage between the gate and the source; since U G =0,U GS =-U S , at this time the drain current I D It is expressed as: According to the first corresponding relationship and the drain current I D Get the source voltage and solve the equation: Solve the source voltage equation to obtain the source voltage U S for: Since the cut-off voltage U Gsoff is less than 0, the source voltage U S satisfy: 0≤U S ≤-U GSoff ; At this time, the source voltage U S The second corresponding relationship is obtained by simplification, namely:

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