CN1099597C - On-line detection method for function of operational amplifier - Google Patents

Abstract

The present invention relates to a method which comprises the steps that two input ends of an operational amplifier are prevented from the short circuit to the ground or a power supply; an inverse-phase input end of the operational amplifier is connected with the output end in a mode of the short circuit; then, a test signal less than the working voltage of the operational amplifier on a circuit board is inputted into a same-phase input end of the operational amplifier; the test signal is taken back from the same-phase input end of the operational amplifier, and a response signal is taken back from the output end; users can deduce whether the open-loop gain of the operational amplifier exists or not according to the coincidence degree of the response signal and the oscillation amplitude output of the operational amplifier permitted by the circuit. In the present invention, the operational amplifier is connected into a follower form in an on-line mode. The gain existence is determined by judging whether the positive input end and the negative input end of the operational amplifier are falsely switched, and thus, the present invention simplifies the test difficulty. Besides, the present invention has the advantage of simple and rapid test.

Description

The on-line testing method of function of operational amplifier

The present invention relates to a kind of method of testing of function of operational amplifier.

A large amount of maintenance practices show, cause in the printed circuit board fault of electronic equipment cisco unity malfunction, the overwhelming majority is caused by the functional fault of active device on the circuit board, therefore, last decade comes, a kind of fault detect instrument that is referred to as " circuit on-line maintenance tester " traditionally, the significant progress of having applied in China can be seen import and the homemade tester that is no less than ten kinds on the home market at present.

The basic fundamental characteristics of this tester, be to adopt " rear drive " and " tracing analysis of device port diagnostic " technology, can " online " on (do not weld from) testing circuit plate the logic function of digital device whether intact, detect whether ports having damage type fault of various digital-to-analog devices, help the user under the situation of not understanding circuit-under-test plate circuit theory, realize the maintenance of components and parts level.

As everyone knows, operational amplifier is to use maximum, a most important analoglike device.But domestic visible on-line maintenance tester all can not carry out online functional test to operational amplifier at present, does not also see the related article of this problem of discussion, thereby feels that generally this tester is not strong to the test function of analog device.

To the implication that operational amplifier can not carry out on-line testing, be meant and judge that operational amplifier also has enough big open-loop gain.The difficult point of this problem is the diversity of operational amplifier type of service and the diversity of the signal of handling.

In view of above-mentioned, the objective of the invention is to propose a kind of on-line testing method of function of operational amplifier.

The object of the present invention is achieved like this:

A kind of on-line testing method of function of operational amplifier the steps include:

(1) two input ends that make operational amplifier are not over the ground and power supply short circuit;

(2) with the inverting input and the output terminal short circuit of operational amplifier;

(3) from the test signal of the operating voltage of the in-phase input end of operational amplifier input less-than operation amplifier on circuit board;

(4) fetch test signal and fetch response signal from the in-phase input end of operational amplifier from output terminal;

(5) according to response signal in the amplitude of oscillation of operational amplifier that circuit allowed output with the degree of agreement of the test signal of fetching from step (4), infer having or not of operational amplifier open-loop gain.

The present invention is with the online form that connects into follower of operational amplifier, and whether empty leading to determined having or not of gain by differentiating the operational amplifier positive-negative input end, simplified difficulty of test, has test advantage simply rapidly.

Below in conjunction with the invention example the present invention is described in detail.

Fig. 1 is operation amplifier circuit figure.

In Fig. 1, have: $\mathrm{VA}=\mathrm{Vo}\frac{Z1}{Z1+Z3},$ $\mathrm{VB}=\mathrm{Vi}\frac{Z4}{Z2+Z4}+\mathrm{Vo}\frac{V2}{Z2+Z4}$

If operational amplifier does not damage, enough big open-loop gain should be arranged, make VA ≈ VB.

Order: Z3=0, Z2=0

Have: VA=Vo, VB=Vi

Can get: Vo ≈ Vi

It is as follows to draw testing procedure thus:

(1) two of operational amplifier input end A points and B point can not be over the ground and power supply short circuit (being that Z1, Z2+Z5 can not be zero), otherwise need manage to disconnect;

(2) with the inverting input A and the output terminal C short circuit of operational amplifier;

(3) from the test signal of the operating voltage of the in-phase input end B of operational amplifier input less-than operation amplifier on circuit board;

(4) the in-phase input end B from operational amplifier fetches test signal and fetches response signal from output terminal C;

(5) according to response signal in the amplitude of oscillation of operational amplifier that circuit allowed output with the degree of agreement of the test signal of fetching from in-phase input end B, infer having or not of operational amplifier open-loop gain.

From as can be known above-mentioned, core of the present invention is with the online form that connects into follower of operational amplifier, and whether void leads to determine having or not of gain by differentiating the operational amplifier positive-negative input end, thereby the on-line testing of realization function of operational amplifier.

Claims (1)

1. the on-line testing method of a function of operational amplifier the steps include:

(1) two input ends that make operational amplifier are not over the ground and power supply short circuit;

(2) with the inverting input and the output terminal short circuit of operational amplifier;

(3) from the test signal of the operating voltage of the in-phase input end of operational amplifier input less-than operation amplifier on circuit board;

(4) fetch test signal and fetch response signal from the in-phase input end of operational amplifier from output terminal;

(5) according to response signal in the amplitude of oscillation of operational amplifier that circuit allowed output with the degree of agreement of the test signal of fetching from step (4), infer having or not of operational amplifier open-loop gain.