JP3033491B2 - Circuit inspection equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection apparatus for an analog circuit device, and more particularly, to an inspection for missing bits of a D / A converter in a LSI for a sound processor for performing digital signal processing, a simple inspection of a distortion factor, and a linearity. The present invention relates to a circuit inspection device for performing inspection or the like of a circuit.

[0002]

2. Description of the Related Art Conventionally, A / D converters, DSPs,
2. Description of the Related Art A sound processor LSI in which a D / A converter and the like are integrated is known. For testing this kind of LSI,
For example, a sine wave signal of 1 kHz is input, and distortion factor measurement is performed to check whether an expected wave output is obtained. A notch filter is typically used for distortion factor measurement. Distortion components can be detected by removing a 1 kHz sine wave signal using a notch filter. As another distortion measurement method, there is a method of visually measuring the distortion with an oscilloscope.

[0003]

In order to accurately measure distortion with a notch filter, a twin T-type notch filter is required. However, even if a twin T-type filter is used, it is difficult to detect a single pulse-like abnormal waveform distortion due to, for example, missing bits of a D / A converter.
Further, test items of this type of LSI include waveform distortion other than the above-mentioned missing bits, noise, and linearity of input / output characteristics. However, there has been no inspection apparatus for simply testing them.

It is an object of the present invention to provide a circuit inspection apparatus which can easily and efficiently perform various inspections of an analog circuit device using a digital tester.

[0005]

SUMMARY OF THE INVENTION The present invention is, firstly, an apparatus for inspecting an analog circuit device by a digital tester, the device being provided for juxtaposing the first and second circuit devices to be inspected. Means, an oscillating means for outputting a sine wave signal, an attenuating means for outputting a voltage obtained by attenuating the output of the oscillating means in a plurality of steps, and one of a plurality of steps of the output voltage from the attenuating means, The first and second
Selecting means for inputting to the circuit devices of the above, and first and second amplifying means for amplifying the outputs of the first and second circuit devices, respectively, with a plurality of steps of gains selected by an instruction from the digital tester. Phase shift means for sequentially and selectively inputting the outputs of the first and second amplifying means and shifting only the fundamental wave component of the output by 180 °;
The waveform distortion inspection adding means for adding the signal shifted by 180 ° to the original signal by the phase shifting means, and the output of the oscillating means to be turned off, the first and second circuit devices having opposite phases to each other. A linearity checking addition means for adding the outputs of the first and second amplifying means when a sawtooth signal is input, and an addition output of the waveform distortion checking addition means or the linearity checking addition means are selected. Input to the digital
A comparison means for pulsing the added output with a reference potential set by an instruction from the tester and outputting an abnormality detection signal sent to the digital tester.

A second aspect of the present invention is an apparatus for inspecting a waveform distortion of an analog circuit device using a digital tester, wherein the oscillation means outputs a sine wave signal, and the output of the oscillation means is attenuated in a plurality of steps. Attenuating means for outputting a voltage, selecting means for selecting one of a plurality of steps of output voltage from the attenuating means in accordance with an instruction from the digital tester and inputting the selected voltage to the circuit device, and an instruction from the digital tester Amplifying means for amplifying the output of the circuit device with a plurality of steps of gains selected by
0 ° phase shift means, and 180 °
Waveform distortion inspection addition means for adding the phase-shifted signal and the original signal, and comparison means for pulsing the output of the addition means with a predetermined reference potential and outputting a waveform distortion detection signal sent to the digital tester It is characterized by having.

In the first and second inventions, preferably,
The phase shifting means is configured by connecting two phase shifting circuits for shifting only the fundamental wave component of the output of the amplifying means by 90 °. More preferably, in the first and second inventions, the phase shift means is connected to three or four phase shift circuits for shifting only the fundamental wave component of the output of the amplifying means by 90 °, and Is to obtain a four-phase output signal whose phase is shifted by 90 °, and the waveform distortion inspection adding means includes:
A first and a second adder for adding signals having a phase shift of 180 ° among the four-phase output signals, and a third adder for further adding the addition results of the first and second adders; It is assumed to be composed of

A third aspect of the present invention is an apparatus for testing the linearity of an analog circuit device by a digital tester, wherein the first and second circuit devices to be tested are serrated in opposite phases to each other. An input means for inputting a signal; an addition means for linearity inspection for adding the output voltages of the first and second circuit devices; and an output voltage of the addition means which is pulsed with a predetermined reference potential to generate the digital signal.
And a comparator for outputting a linear distortion detection signal caused by a difference in linearity between the first and second circuit devices sent to the tester.

According to the first aspect of the invention, various tests of circuit devices such as a sound processor LSI are shared by, for example, modularizing a circuit unit capable of handling each test, so that test circuits are separately provided for different tests. It can be done simply and efficiently using a digital tester without any preparation. For example, the bit missing inspection of the D / A converter is sequentially performed on two circuit devices to be inspected. That is, a sine wave signal is supplied to the circuit device, and the fundamental wave component of the output signal is shifted by 180 degrees by the phase shift means.
The phase-shifted signal is added to the 180 ° phase-shifted signal and the original signal by the waveform distortion inspection addition means to extract a pulse-like high-frequency distortion component due to missing bits, which is further digitized by the comparison means to obtain a distortion detection signal. Can be obtained.

Further, if the 180 ° phase shift means is constituted by two stages of 90 ° phase shifters, the output of the waveform distortion test addition means will include low frequency distortion components as well as high frequency distortion components. By simply switching the reference potential of the comparing means and performing the same processing, a simple inspection of low-frequency distortion or noise level (that is, determination of presence / absence of distortion, which is not strict distortion rate measurement) can be performed. That is, by setting the switching of the reference potential of the comparing means, a pulse-like high-frequency distortion, a low-frequency distortion of a predetermined level or more, and a waveform distortion including noise caused by missing bits of the D / A converter are digitally processed in a series of inspection processes. Can be detected and determined.

The above-mentioned bit missing or distortion factor inspection does not use the linearity inspection addition means. Regarding the linearity test, which is one of the conversion performances of the D / A converter, a saw-tooth wave voltage having an opposite phase to each other is inputted to the juxtaposed first and second circuit devices without using the oscillation means and the attenuation means. Then, the output voltages are added by the linearity inspection addition means, and the added output is similarly pulsed by the comparison means, whereby the linearity caused by the difference in linearity between the first and second circuit devices is obtained. A distortion detection signal can be output.

According to the second aspect of the present invention, the input side of the circuit device to be inspected is provided with attenuating means for outputting a voltage attenuated in a plurality of steps, and the output side of the circuit device has a plurality of steps of gain. Amplifying means for amplifying the output of the circuit device, even when various input signal levels for the circuit device to be inspected are selected, without adjusting the reference potential of the comparing means for performing abnormality determination, always in a fixed determination range. Inspection can be performed.

According to the third aspect of the present invention, since the linearity of two circuit devices to be inspected is compared, it is determined separately which one is defective in the case of a defect. Simultaneous inspection is possible, so that the time required for product screening and the like can be greatly reduced.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of a circuit inspection apparatus according to one embodiment of the present invention. Device mounting means 1
Include the first and second to be tested by the digital tester 2.
The second two circuit devices 3 (3a, 3b) are mounted side by side. In this embodiment, the circuit device 3 is an L for a sound processor as shown in FIG.
An A / D converter for converting an input analog signal Ain into a digital signal, a DSP for processing the converted digital signal, and a D / A converter for converting the processed signal into an analog signal Aout and outputting the analog signal Aout Including.
This LSI can receive a digital signal Din as shown in FIG.

Each circuit on the input side and the output side of the circuit device 3 is modularized for each block shown in FIG. On the input side, an oscillator 4 whose oscillation frequency and output level are controlled by the digital tester 2 to output a sine wave signal, an attenuator 5 for attenuating the output signal of the oscillator 4 in a plurality of steps, and an attenuator 5 Selection means 6 is provided for selecting a signal of a predetermined attenuation level from the output and inputting the signal to the circuit device 3.

As shown in FIG. 3, the attenuator 5 comprises an input buffer 31, a resistance attenuator 32, and an output buffer 33 for outputting eight steps of outputs A1, A2,..., A8. . Specifically, in the case of the embodiment, 0 dB
An output voltage attenuated in steps of -6 dB up to -42 dB can be obtained.

As shown in FIG. 4, the selecting means 6 is arranged in accordance with the output of each step from the attenuator 5, and is, for example, a CMOS analog transfer gate 41 (411, 4).
.., 418) and these transfer gates 41 are connected to the 3-bit control signals B1, B from the digital tester 2.
2, a decoder 42 for selectively turning on according to B3 (corresponding to the control signal in FIG. 1), and a buffer amplifier 43 for extracting a selected voltage. The 3-bit control signals B1, B2, and B3 are CMOS levels of positive logic, and as shown in Table 1 below, one of the outputs of the attenuator 3 having a step of -6 dB is selected, and the circuit to be inspected is selected. It is supplied to the device 3.

[0018]

[Table 1]

The output terminal of the circuit device 3
/ A converter 7 (7a, 7b) is provided. This is to be used when the circuit device 3 is an A / D converter having no D / A converter in the output stage.
The characteristics are accurate. Switch circuits SWa and SWb for switching the output of the circuit device 3 and the output of the D / A converter 7 under the control of the digital tester 2 are provided, and the signals selected by these switch circuits SWa and SWb are bit clock signals, respectively. It is supplied to a filter 8 (8a, 8b) for removing components.

At the subsequent stage of the filter 8, there are provided amplifiers 9 (9a, 9b) for amplifying the output of the circuit device 3 with a plurality of steps of gain that can be arbitrarily selected according to an instruction from the digital tester 2. This is because the input level to the circuit device 3 can be switched, but a signal of a constant level of 0 dB is given to a subsequent circuit that determines good or bad regardless of the input level.

As shown in FIG. 5, the amplifiers 9a and 9b each have two stages of variable gain amplifiers 51 and 52 each having a gain adjuster, and control of three bits each from the digital tester 2. A decoder 53 for decoding signals C1, C2,..., C6 (corresponding to the control signal in FIG. 1) and performing gain control, and an output buffer 54. The 6-bit control signals C1, C2,..., C6 are CMOS levels of positive logic, and the gain is controlled according to, for example, Table 2 below.

[0022]

[Table 2]

The output of the amplifier 9 is transferred to a different route depending on the inspection item. In a route for inspecting waveform distortion including bit omission of the circuit device 3, outputs of the two amplifiers 9 are switched by the switch circuit SW3 and sequentially and selectively input, and only the fundamental wave component is shifted by 180 °. A phase means 10 is provided. Further, an adder 12 for waveform distortion inspection which adds the signal shifted by 180 ° by the phase shifter 10 and the original signal, and a digital tester 2 which pulsates the added output of the adder 12 with a predetermined reference potential and outputs Is provided with a comparison means 13 for outputting an abnormality detection signal sent to the microcomputer. The adding means 12 and the comparing means 13 are integrally modularized.

As shown in FIG. 6, the phase shift means 10 is composed of four phase shift circuits 61a, 61b, 61c and 61d for shifting only the fundamental wave component of the output of the amplifier 9 by 90 °. It is connected to and configured. These phase shift circuits 61a
To 61d are, for example, as shown in FIG.
And the resistors R1 to R3 and the capacitor C. For example, when the fundamental frequency is f0 = 1 kHz, in FIG. 7, the values of the resistors and the capacitors are set so as to satisfy 2 kΩ ≦ R1 ≦ 1 MΩ, f0 = １ ／ πCR3, 2 kΩ ≦ R3 ≦ 1 MΩ.

As a result, as shown in FIG.
The phase of the kHz component is shifted by 90 °, and the phase shift amount is 180 at the frequency of 0.
Thus, a phase shift characteristic in which the phase shift amount is 0 ° at ° and frequency Δ is obtained. Therefore, the output signal D1 of the first-stage phase shift circuit 61a,
The output signal D3 of the third-stage phase shift circuit 61c has a fundamental component shifted by 180 °. Similarly, the output signal D2 of the second-stage phase shift circuit 61b and the fourth-stage phase shift circuit 61d
The output signal D4 has a fundamental wave component shifted by 180 °.

The waveform distortion inspection addition means 12 includes the phase shift means 1
The four-phase output signal of phase shifter 10 is used for extracting bit missing components and low-frequency distortion components by adding the four-phase output signals of 0 whose phases are shifted by 180 °, and as shown in FIG. Of these, a first addition circuit 91a for adding the output signals D1 and D3, a second addition circuit 91b for adding the output signals D2 and D4, and a third addition circuit 91c for further adding the addition results Have been.

Here, the two adding circuits 91a and 91b basically output the same output, and any one of them may be used in principle. When only one of the adders 91a and 91b is used, the third adder 91c is not required. In this embodiment, by providing the first and second adder circuits 91a and 91b in parallel, gain is obtained for the distortion component to be extracted, and at the same time, the unnecessary noise component generated only on one side is affected by averaging. Can be reduced, thereby increasing the accuracy of waveform distortion detection.

The output of the waveform distortion inspection addition means 12 is:
Once taken out of the module, it is selected by the switch circuit SW4 controlled by the digital tester 2 and input to the comparing means 13. The comparing means 13 is shown in FIG.
As shown in FIG.
It is composed of two comparators 92a and 92b to which F2 (REF1 <REF2) is given, and an OR gate 93 that takes the logical sum of their outputs.
Is a window comparator for detecting a component out of the range. The reference potential REF of this window comparator
1 and REF2 are generated by a reference potential setting circuit 94 variably controlled by a DC voltage (VR = 1V to 10V) from the digital tester 2. Specifically, in the reference potential setting circuit 94, the input DC voltage VR is converted into a current and then into a very small voltage, for example, REF1 = 10 m
V-100mV, REF2 = 100mV-1000mV
The reference potential is set in the range of. In addition, by changing the gain of the adding means 12 separately from the reference potential range of the comparing means 13, it is also possible to apparently change the range of pulse formation.

In the case of the linearity test, the oscillator 4 is turned off and the sine wave signal is not supplied to the first and second circuit devices 3a and 3b, but the sawtooth wave digital data from the digital tester 2 is used instead. Each circuit device 3a, 3b
And 10 Hz in opposite phases as shown in FIG.
The output voltages S1 and S2 in the form of sawtooth waves of about 100 Hz are generated. These negative phase output voltages are added by the linearity inspection addition means 11. The result of the addition by the adding means 11 is selected by the switch circuit SW4 and input to the comparing means 13, which is also pulsed at a predetermined reference potential to obtain the difference between the linearity of the first and second circuit devices 3a and 3b. And outputs a linear distortion detection signal caused by the above. A similar linearity test can be performed by separately installing an analog sawtooth wave generating means and inputting an analog signal to the first and second circuit devices 3a and 3b and inputting an opposite-phase sawtooth wave. It is.

The principle operation of a circuit distortion inspection including a missing bit in the circuit inspection apparatus thus configured will be described with reference to FIG. This waveform distortion inspection is sequentially performed on each of the two juxtaposed circuit devices 3a and 3b one by one as described above. FIG. 10 shows operation waveforms when the output of the one circuit device is sent to the phase shift means 10. It is assumed that the output signal D1 of the first-stage phase shift circuit 61a includes, for example, high-frequency distortion components N1 and N2 due to missing bits as shown in the figure. Since these high-frequency distortion components are not phase-shifted, the output signals D3 of the third-stage phase shift circuit 61c also include similar distortion components N1 and N2. These output signals D
For 1, D3, only the fundamental wave component is shifted by 180 °,
When added by the waveform distortion inspection addition means 12, the fundamental wave component is canceled as shown in the figure, and the high frequency distortion components N1, N
2 and only the low-frequency distortion component N0 are extracted.

The pulse-like high-frequency component caused by missing bits can be detected by, for example, passing through a 180 ° phase shifter set at f0 = 1 kHz and adding the original signal. is there. However, in this case, distortions having a frequency lower than 1 kHz are inverted with respect to each other and added to cancel each other, and cannot be detected. In this embodiment, not only a pulse-like high-frequency component but also a low-frequency distortion component can be detected by passing the signal through two stages of a 90 ° phase shift circuit and adding the original signal.

The result of the addition by the adding means 12 is represented by a window
In comparison means 13 constituting a comparator, FIG.
By pulsing with two reference potentials REF1 and REF2 as shown in (1), an abnormality detection signal in which high-frequency distortion components N1 and N2 are detected can be obtained. This detection signal is sent to the digital tester 2, and for example, when "H" is detected within a predetermined time, it is determined that NG is output. With respect to the low frequency distortion component and the noise component shown in FIG. 10 as well, abnormality detection can be performed by switching and setting the reference potential of the comparison means 13 and performing the same operation.

FIG. 12 is a diagram showing a digital signal of a series of inspection processing.
The test flow on the tester 2 side is simply shown. First
The second two circuit devices to be tested are set (S
1) First, a bit missing check is performed (S2), and the pass / fail is determined (S3). Next, a distortion factor inspection is performed (S4), and a pass / fail judgment is similarly made (S5). Thereafter, a noise level test (S6) and its pass / fail judgment (S7) are sequentially performed, and a linearity test (S8).
And the pass / fail judgment (S9) are repeated, and the non-defective judgment processing (S9)
10) or a defect determination process (S11).

FIG. 13 is a more specific processing flow of the bit missing inspection. In the initial setting step S21, FIG.
Switch circuits SW1, SW2, SW3 and SW4 shown in FIG.
Is switched to the contact a side (control signal ,,), and the oscillator 4
Of the frequency and output level (control signal), the setting of the attenuation level by the selection means 6 (control signal), the amplifier 9
(Control signal), and the reference potentials REF1 and REF2 of the comparing means 13 (DC voltage = VR).

Then, under the initially set conditions, the first circuit device 3a is inspected (S22), its pass / fail judgment is made (S23), and the number of inspections is judged (S2).
4) If the predetermined number has not been reached, the selecting means 6
By switching the amount of attenuation in the amplifier and the gains of the amplifiers 9a and 9b (S2
5) The same inspection is repeated a predetermined number of times. After performing a predetermined number of inspections on the first circuit device 3a, the switch circuit SW3 is switched to the contact b side, and the conditions of the selection means 6 and the amplifier 9 are initialized (S26). The same inspection is repeated a predetermined number of times by switching the input level (S27 to S30). The same processing flow also applies to the simple distortion factor test and the noise level test, except that the reference potential setting condition of the comparing means 13 is different.

FIG. 14 shows a processing flow of the linearity inspection. In the initial setting step S41, the switch circuits SW1 and SW2 are set to the a contact side (control signal), and the switch circuit SW4 is set to the b contact side (control signal).
A digital saw-tooth wave is generated (data), the oscillator 4 is turned off (control signal), the attenuation level is set by the selection means 6 (control signal), the gain of the amplifier 9 is set (control signal), and the comparison means 13 is set. Reference potentials REF1, REF
Set 2 (DC voltage). Then, an inspection determination is performed based on the linearity abnormality detection signal (S42, S43). Note that the noise inspection can be performed according to the same processing flow as the linearity inspection.

As described above, according to this embodiment, a module test circuit is used in common, and a digital tester is used to eliminate bit distortion and distortion in analog input / output circuit devices such as sound processor LSIs. rate,
Various inspections such as noise level and linearity can be efficiently performed, so that inspection time can be reduced and inspection cost can be reduced. Further, an attenuator capable of selecting a plurality of steps of attenuation is provided on the input side of the circuit device, and an amplifier capable of selecting a plurality of steps of gain so as to return the amount of signal attenuation on the input side is provided on the output side. Therefore, the waveform distortion test including missing bits has an advantage that even if the input level to the circuit device is variously changed, it is not necessary to adjust the range of the comparison means for performing the abnormality determination.

In this embodiment, a four-phase output signal having a 90 ° phase shift is obtained as a phase shift means for waveform distortion inspection, and the four-phase output signal is added to the waveform distortion inspection addition means. A first adder and a second adder for adding signals having phases opposite to each other among the output signals are provided in parallel, and a third adder for further adding these addition results is provided. Thus, the addition gain can be increased for the waveform distortion component to be detected, and unnecessary noise components can be reduced by averaging. Therefore, highly accurate waveform distortion inspection can be performed. Furthermore, since the linearity inspection is performed by comparing two circuit devices, it is possible to effectively reduce the inspection time.

The present invention is not limited to the above embodiment. For example, as shown in FIG.
90 ° phase shift circuits 151a, 151b and 151c
Can also be used. That is, the original signal is used as it is as one output signal D1 at 90 ° as in the previous embodiment.
It is possible to obtain four-phase output signals D1 to D4, each of which is out of phase. Further, as shown in FIG. 16, the 90 ° phase shift circuit may have a configuration in which the arrangement of the resistor R3 and the capacitor C is reversed from that in FIG. The phase shift characteristics shown in FIG. 17 can be obtained by setting the respective resistors and capacitors under the same conditions as in the previous embodiment. Therefore, by connecting these phase shift circuits in cascade in two stages and adding the original signal and the 180 ° phase shift signal, high frequency distortion components and low frequency distortion components can be extracted in the same manner as in the previous embodiment.

Further, in the case of an A / D-only circuit device, it can be dealt with by switching the switch circuits SW1 and SW2 to the contact b side and inserting D / A converters 7a and 7b in the output stage. Can be handled by installing an A / D converter having accurate characteristics in the input stage or by inputting a digital waveform from the digital tester 2. A / D, D /
The present invention can be similarly applied to inspection of the distortion factor, linearity, and noise level of various analog circuit devices other than A.

[0041]

As described above, according to the present invention, it is possible to obtain a circuit inspection apparatus that can easily and efficiently perform various inspections of an analog circuit device using a digital tester. In particular, by providing an attenuator capable of selecting a plurality of steps of attenuation on the input side of the circuit device and providing an amplifier capable of selecting a plurality of steps of gain so as to return the signal attenuation on the input side on the output side, the waveform distortion can be reduced. Regarding inspection, even if the input level to the circuit device is variously changed,
Range adjustment by comparison means for performing abnormality determination can be eliminated. Further, the linearity inspection is performed by comparing two circuit devices, thereby shortening the inspection time.

[Brief description of the drawings]

FIG. 1 shows a configuration of a circuit inspection apparatus according to an embodiment of the present invention.

FIG. 2 shows an example of a circuit device to be inspected by the apparatus.

FIG. 3 shows a configuration of an attenuator in the device.

FIG. 4 shows a configuration of a selection unit in the apparatus.

FIG. 5 shows a configuration of an amplifier in the device.

FIG. 6 shows a configuration of a phase shift means in the apparatus.

FIG. 7 shows a configuration of a 90 ° phase shift circuit used for the phase shift means of FIG. 6;

FIG. 8 shows phase shift characteristics of the phase shift circuit of FIG. 7;

FIG. 9 shows a configuration of a waveform distortion inspection adder and a comparator in the same device.

FIG. 10 is a waveform chart for explaining an operation of a waveform distortion inspection by the apparatus.

FIG. 11 shows a sawtooth signal used for a linearity test by the apparatus.

FIG. 12 shows a processing flow on the digital tester side of the apparatus.

FIG. 13 shows a processing flow of a missing bit check.

FIG. 14 shows a processing flow of a linearity test.

FIG. 15 shows a configuration of a phase shift unit of another embodiment.

FIG. 16 shows a configuration of a 90 ° phase shift circuit of another embodiment.

17 shows a phase shift characteristic of the phase shift circuit of FIG.

[Explanation of symbols]

1: Device mounting means, 2: Digital tester, 3
a, 3b: circuit device to be inspected, 4: oscillator, 5 ...
Attenuator, 6 ... selecting means, 7a, 7b ... D / A converter, 8a, 8b ... filter, 9a, 9b ... amplifier, 10
... Phase shift means, 11 ... Addition means for linearity inspection, 12 ... Addition means for waveform distortion inspection, 13 ... Comparison means, SW1 to SW4 ...
Switch circuit.

Claims (5)

(57) [Claims] 1. An apparatus for testing an analog circuit device using a digital tester, comprising: device mounting means for juxtaposing first and second circuit devices to be tested; and oscillating means for outputting a sine wave signal. An attenuating means for outputting a voltage obtained by attenuating the output of the oscillating means in a plurality of steps; and selecting one of the plurality of steps of the output voltage from the attenuating means in accordance with an instruction from the digital tester to select the first and the second output voltages. Selecting means for inputting to the second circuit device; and first and second amplifying means for amplifying outputs of the first and second circuit devices, respectively, with a plurality of steps of gains selected by an instruction from the digital tester. Phase shift means for selectively inputting the outputs of the first and second amplifying means sequentially and shifting only the fundamental wave component of the output by 180 °; A waveform distortion inspection adding means for adding the signal shifted by 180 ° to the original signal by the phase shifting means; and turning off the output of the oscillating means to the first and second circuit devices. A linearity checking addition means for adding the outputs of the first and second amplifying means when a sawtooth signal is input; and an addition output of the waveform distortion checking addition means or the linearity checking addition means. And a comparison means for pulsating the added output with a reference potential set by an instruction from the digital tester and outputting an abnormality detection signal sent to the digital tester. Circuit inspection equipment. 2. An apparatus for inspecting a waveform distortion of an analog circuit device using a digital tester, comprising: oscillating means for outputting a sine wave signal; and attenuating means for outputting a voltage obtained by attenuating the output of the oscillating means in a plurality of steps. Selecting means for selecting one of a plurality of output voltages from the attenuating means in accordance with an instruction from the digital tester and inputting it to the circuit device; and selecting a plurality of steps in accordance with an instruction from the digital tester. Amplifying means for amplifying the output of the circuit device with a gain of: phase shifting means for shifting only the fundamental wave component of the output of the amplifying means by 180 °; and a signal 180 ° shifted by the phase shifting means and the original signal. A waveform distortion inspection adding means for adding a signal to the digital tester; Circuit testing apparatus characterized by comprising a comparison means for outputting a waveform distortion detection signal sent. 3. The phase shifter according to claim 1, wherein the phase shifter is configured by connecting two phase shifters for shifting only the fundamental wave component of the output of the amplifier by 90 °. The circuit inspection device according to 1. 4. The phase shift means comprises three or four phase shift circuits for shifting only the fundamental wave component of the output of the amplification means by 90 °.
And a four-phase output signal whose fundamental component is shifted by 90 ° from each other to obtain a four-phase output signal. First and second to add
The circuit inspection apparatus according to claim 1, further comprising: an addition circuit of (1) and a third addition circuit that further adds the addition results of the first and second addition circuits. 5. An apparatus for inspecting the linearity of an analog circuit device by a digital tester, comprising: input means for inputting sawtooth signals having phases opposite to each other to first and second circuit devices to be inspected which are juxtaposed. A linearity check adding means for adding output voltages of the first and second circuit devices; and a first voltage which is output to the digital tester by pulsing an output voltage of the adding means with a predetermined reference potential. And a comparing means for outputting a linear distortion detection signal caused by a difference in linearity of the second circuit device.