JPS63182576A - Device for diagnostic deterioration of operational amplifier - Google Patents

Abstract

PURPOSE:To attain the diagnosis of deterioration without detaching an operational amplifier from a printed board, to facilitate a diagnosing operation, and to shorten the diagnosing time by displaying the result of comparison of the distortion degree of a signal and a reference value. CONSTITUTION:When an input signal to the operational amplifier 1 as the object of deterioration diagnosis is held at zero, an internal noise signal in the amplifier 1 is inputted to a computing element 5 through a BPF 3 and an amplifier 4 to calculate the distortion degree of the internal noise signal. A comparison reference setter 7, on the other hand, evaluates the distortion rate of the internal noise of a normal operational amplifier and sets a value twice as large as its dispersed value as a comparison reference value. A comparator 6 judges the deterioration of the amplifier 1 when the distortion degree of the internal noise of the computing element 5 exceeds the comparison reference, and displays the result on a display device 8.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is an operational amplifier that has been degraded due to surges or the like being applied to its input terminal, and which exhibits operational fieency equivalent to that of a normal operational amplifier. The present invention relates to an operational amplifier deterioration diagnostic device that determines a deteriorated operational amplifier.

[Conventional technology]

Fig. 2 is a circuit diagram showing a conventional operational amplifier deterioration diagnostic device. 11 is an operational amplifier to be diagnosed, and 12 is an ammeter for measuring the input bias current, which is connected to the input terminal of the operational amplifier 11 via a resistor R. has been done. As shown in the figure, resistors are also connected to the input terminal and feedback circuit of the operational amplifier 11 that I received.

Next, the second operation will be explained.

First, the operational amplifier 11 K' is connected to the source (+Vcc, -Vc
c) and the input signal voltage and input offset are 0.
When the output voltage of the operational amplifier 11 is 0, the DC input current is measured. The DC input current obtained in this way is the input bias current, and this is compared with the input bias current previously measured in the same manner as above for a normal operational amplifier. If there is a large error between these measured values, it is determined that the operational amplifier to be diagnosed has deteriorated. judge that it is.

FIG. 3 is a circuit diagram showing another conventional deterioration diagnosing device.

In the figure, 11 is an operational amplifier to be diagnosed, and 13 is a voltmeter used to calculate the input offset current, which is connected to the output terminal of this operational amplifier 11. 1
4.15 is an interlocking type switch that is opened and closed when calculating the input offset current.
Short-circuit or open the resistor 1 connected to the input terminal and the resistor 8 connected to the input terminal. Furthermore, one resistor R1, which is different from the resistor R1°8, is additionally connected to each of the e input terminal and the (2) input terminal.

几2 is a feedback resistor that determines the amplification factor.

Next, the operation will be explained.

First, apply power to the operational amplifier 11 (-1-Vcc, -Vc
c) is applied, the voltage when the switches 14 and 15 are closed is measured with the voltmeter 13, and the measured value E1 is read. Next, the voltage when the switches 14 and 15 are opened A is similarly measured with the voltmeter 13, and the measured value E2 is read. Using the measured values El and E2 thus obtained, the input offset current Ios is calculated according to (1) 2.

In other words, when the operational amplifier 11 deteriorates due to surge input, etc., there is no difference between normal operational amplifiers and normal operational amplifiers in terms of amplification and first-order delay operations.
The input offset current that is the calculation result of the above equation (1) causes a large error with respect to a normal operational amplifier. Therefore, when this error occurs, the operational amplifier 11 to be diagnosed
is judged to have deteriorated.

[Problem that the invention seeks to solve]

Conventional operational amplifier deterioration diagnostic equipment is configured as described above, so in order to measure input bias current and input offset current, it is necessary to prepare a measurement circuit consisting of multiple components according to each of these current definitions. However, in order to diagnose the deterioration of an operational amplifier mounted on a printed board, it is necessary to remove the operational amplifier to be diagnosed from the printed board and connect the circuit as shown in Figure 2 or Figure 3. The work of removing the solder and attaching it again became extremely troublesome. In addition, there are also problems in that the above-mentioned work may cause deterioration or failure of the operational amplifier to be diagnosed.

This invention was made to solve the above-mentioned problems. It is possible to diagnose the deterioration of an operational amplifier mounted on a printed circuit board without removing it from the printed board, and it also simplifies the diagnostic operation and can be carried out in a short time. The purpose of this invention is to obtain a deterioration diagnostic device for operational amplifiers.

[Failure to solve the problem]

The operational amplifier deterioration diagnosis device according to the present invention extracts the internal noise generated inside the operational amplifier to be diagnosed through a band-pass filter, calculates the degree of distortion of the internal noise using a calculator, and sets a standard in advance. The skewness of the normal operational amplifier is compared with the skewness of the internal noise of the normal operational amplifier, the deterioration of the operational amplifier to be diagnosed is determined, and the determination result is displayed on the display device.

[For production]

The output signal of the operational amplifier targeted for deterioration diagnosis according to this invention is the one obtained when the input signal of this operational amplifier is set to 0.The bandpass filter cuts off the DC component of the output signal and passes an appropriate frequency component. The amplifier amplifies the signal that has passed through the band-pass filter to an appropriate size, the arithmetic unit calculates the distortion of the signal obtained by this amplifier, and the skewness comparator compares the result calculated by the above arithmetic unit with the one in advance. A comparison is made with a predetermined comparison standard, and the comparison result is displayed on a display device, thereby making it possible to determine the deterioration of an operational amplifier to be degraded while it is mounted on a printed circuit board or the like.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, reference numeral 1 denotes an operational amplifier to be diagnosed for deterioration whose input is short-circuited during diagnosis, which is mounted on a printed board or the like and constitutes a part of a predetermined circuit device. 2
is the output signal of the operational amplifier 1 targeted for deterioration diagnosis, and 3 is a bandpass filter that passes a signal in a predetermined frequency band among this output signal, and the frequency band to be passed depends on the type of operational amplifier 1 targeted for deterioration diagnosis. decided,
For example, the lower limit cutoff frequency fo = 0.01 Hz and the upper limit cutoff frequency f 1 = 20 Hz. 4 is an amplifier that amplifies the signal obtained from the band pass filter 3; 5 is an arithmetic unit that calculates the distortion of internal noise using the signal obtained from the amplifier; 7 is a comparison standard for determining deterioration. It is a comparison standard setting device. An operational amplifier defined as normal is used to set the comparison standard, and the skewness of the internal noise of the normal operational amplifier, which is determined in advance by the arithmetic unit 5, is calculated. Then, the skewness of a plurality of normal operational amplifiers is further evaluated and a comparison standard is set. For example, the dispersion value of the distortion of a normal operational amplifier is calculated, twice this dispersion value is used as a comparison standard, and anything exceeding this value is determined to be degraded. 6 is the above computing unit 5
8 is a display means for displaying the comparison result output from the skewness comparator 6; 9 is a display means for displaying the comparison result output from the skewness comparator 6; Printing means prints out the comparison results output from the skewness comparator 6, and numeral 10 denotes audio notification means for audibly announcing the comparison results output from the skewness comparator 6.

Next, the operation will be explained.

First, a power supply is connected to the operational amplifier 1 to be diagnosed for deterioration, and the input signal is set to O by short-circuiting the input. Then, this operational amplifier 1 outputs an output signal having internal noise. This output signal is input to a band pass filter 3 to remove the DC component, and only a signal in a predetermined frequency band is input to an amplifier 4. The amplifier 4 amplifies this input signal and then inputs it to the arithmetic unit 5, which calculates the degree of distortion of internal noise in the output signal output from the amplifier.

On the other hand, the comparison standard setter 7 calculates in advance the skewness of the internal noise of a normal operational amplifier (not shown) using the same method as above,
Evaluate this calculation result for multiple normal operational amplifiers,
This is taken as the skewness of the internal noise, and for example, the value twice this variance value is used as a comparison standard. Next, this comparison standard and the skewness of the internal noise which is the output of the arithmetic unit 5 are input to the comparator 6,
It is determined whether this skewness exceeds the comparison standard. If it is determined that the operational amplifier 1 has deteriorated, it is displayed on the display device 8, printed out using the printing device 9 as necessary, and outputted as a sound using the audio notification device 10. do.

In this way, the deterioration test can be performed with the operational amplifier 1 mounted on a printed circuit board, etc., and the work related to the test can be performed easily and quickly. can.

In the above embodiment, the set comparison standard is twice the variance of the distortion of the output signals of a plurality of normal operational amplifiers.
It may be 1.5 times or 3 times this value.

Alternatively, the maximum value of the distortion variance values of the output signals of a plurality of normal operational amplifiers may be set as the comparison standard.

In addition, in the configuration of the operational amplifier deterioration diagnosis device, the amplifier 4 is connected after the bandpass filter 3, but if the frequency characteristics obtained by the bandpass filter 3 and the amplifier 4 are the same, various connection methods can be considered. It will be done. For example, the same effect can be obtained by connecting the bandpass filter 3 after the amplifier 4, or by connecting a bypass filter, an amplifier, and a low-pass filter in this order.

〔Effect of the invention〕

As described above, according to the present invention, the internal noise generated inside the diagnostic operational amplifier is extracted through a band-pass filter, the skewness of the internal noise is calculated by a calculator, and this result is used as a reference in advance. Compare the skewness of the internal noise of the normal operational amplifier with the skewness comparator that you have set,
Since the configuration is configured to determine the deterioration of the operational amplifier to be diagnosed and display it on the display device, it is possible to diagnose the deterioration without removing the operational amplifier to be diagnosed from the printed circuit board, etc., as well as shorten the diagnosis time and improve reliability. This has the effect of not only making it possible to perform a certain diagnosis, but also requiring no special skills for the diagnosis.

[Brief explanation of the drawing]

FIG. 1 is a block connection diagram showing an operational amplifier deterioration diagnosing device according to an embodiment of the present invention, and FIGS. 2 and 3 are circuit diagrams showing conventional operational amplifier deterioration diagnosing devices. 1 is an operational amplifier targeted for deterioration diagnosis! , 2 is an output signal of an operational amplifier, 3 is a bandpass filter, 4 is an amplifier, 5 is an arithmetic unit, 6 is a distortion comparator, 7 is a comparison standard setting device, and 8 is a display means. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Patent applicant: Mitsubishi Electric Corporation (2 others)

Claims (1)

[Claims] An operational amplifier to be diagnosed whose input is short-circuited, a bandpass filter that passes a predetermined frequency component of the output signal of the operational amplifier to be diagnosed, an amplifier that amplifies the signal obtained from this bandpass filter, and this amplifier. a computing unit that computes the skewness of internal noise in the output signal obtained from the computing unit; a skewness comparator that compares the output signal from this computing unit with a preset comparison standard; An operational amplifier deterioration diagnostic device comprising: a display device that displays comparison results;