JPS5813866B2 - Operating characteristic measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for measuring operating characteristics, and particularly to an apparatus for measuring operating characteristics of a device or element under test, such as a sample-and-hold circuit, with high precision.

High-speed operational amplifier (operational amplifier) and high-resolution digital
It may be desirable to measure or test the settling time of an analog converter (DAC) or the operating characteristics of a device or element, such as a sample-and-hold (S/H) circuit, including the switching (or sampling) operation.

The characteristics of these devices are generally measured using an oscilloscope or, for high-speed devices, a sampling oscilloscope.

However, since conventional measurement devices use analog circuits such as amplifiers, their frequency distortion, waveform distortion,
In addition to being influenced by drift and non-linear distortion, the measurement accuracy is only a few, making it impossible to accurately measure the characteristics of the device under test, which has a high accuracy of, for example, about 0.1%.

Particularly in the case of S/H circuits, it is preferable to measure not only static characteristics but also dynamic characteristics by actually operating at high speed.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a novel operating characteristic measuring device capable of measuring dynamic operating characteristics of an electrical device or element with high precision and high speed.

Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings.

In FIG. 1, 110 is an input terminal, and this input terminal 10
In addition, a periodic input signal of a known waveform, for example, is sent to the comparator 12 via an input circuit (not shown) including an attenuator, a buffer amplifier, etc. as necessary, and a device under test 13, which is an S/H circuit, for example. is supplied to the non-inverting input terminal of

11 is an external trigger terminal.

The inverting input terminal of this comparator 12 has DA as a reference input.
Provides a stepped reference voltage from C14.

The output of this comparator 12 is then supplied to a Z-axis (luminance control axis) amplifier 16.

This Z-axis (brightness control axis) amplifier 16 amplifies the output of the comparator 12 to a desired polarity and amplitude and supplies it to the brightness modulation electrode of the electron gun of the CRT 18, such as a control grid, cathode, or planking deflection plate.

Further, the output of the DAC 14 is applied to a vertical amplifier 20 to convert it into a push-pull output, and then supplied to the vertical deflection plate of the CRT 18.

Moreover, the time axis circuit 22 is the circuit shown in FIG.
A push-pull low-speed slope or staircase wave signal that drives the horizontal deflection plate of the CRT 18, a high-speed slope signal that is generated in synchronization with the input signal, and a high-speed slope signal that is generated in synchronization with the input signal, and when these two signals match, the comparator 1
A strobe pulse with a narrow pulse width is generated to drive 2.

Here, the digital processing circuit 24 is a circuit added to store and perform arithmetic processing on the digital signals that are the outputs of the DAC 14 and the comparator 12.

Next, the operation of the apparatus shown in FIG. 1 will be explained with reference to FIGS. 2 to 4.

2 is a waveform diagram for explaining the outline of the operation of the device shown in FIG. 1, especially the operation of the time base circuit 22, and FIG. 3 is a waveform diagram for explaining the details, especially the operation of the comparator 12. FIG. 4A shows a part of the display on the CRT screen, and FIG. 4B shows an example of the waveform displayed on the CRT screen.

First, what is shown in FIG. 2A is the CR
A slow ramp (sweep) signal applied to one of the T18 horizontal deflection plates that occurs at a selectable constant period.

Shown at 21''-zB is the reset pulse for the slow ramp signal shown in FIG. 2A.

What is shown in FIG. 2C is a high speed ramp signal that is generated in synchronization with the input signal, and has a frequency several hundred to several thousand times higher than that of the slow ramp signal shown in FIG. 2A.

In the circuit shown in FIG. 2D, a pulse generation circuit including a comparator (not shown) in the time base circuit 22 generates a high-speed ramp signal shown in FIG. 2C and a slow ramp signal shown in FIG. 2A. These are narrow pulse width strobe pulses that occur at coincident points.

What is shown in FIG. 2E is the reference voltage output from the DAC 14, and the reference voltage is changed bit by bit every time the reset pulse (FIG. 2B) for the low-speed ramp signal shown in FIG. 2A is generated. increase (or decrease).

The reference voltage waveform shown in FIG. ) is scanned.

Here, when the output from the comparator 12 is not applied to the Z-axis amplifier 16, this scanning line has a constant brightness, so the entire scanning range of the screen emits light uniformly brightly (or darkly).

However, in reality, the two signals of "H" and "L" from the comparator 12
Since the value voltage is applied, the output signal of the device under test 13 and the DA
Each scanning line is modulated to produce brightness and darkness depending on the magnitude relationship with the reference voltage of C14.

This will be explained below with reference to FIG.

FIG. 3A shows an example of the input signal to the comparator 12, and is a waveform diagram showing the voltage magnitude (vertical axis) as a function of time (horizontal axis).

In the figure, ■1, ■2 and ■3 are the DAC 1 shown in Figure 2E.
This is superimposed to show the relationship between the reference voltage from No. 4 and the input signal.

What is shown in FIG. 3B is the strobe pulse shown in FIG. 2D, which is applied to the comparator 12 and the device under test 13.

And those shown in Figure 3 C, D, and E are DA
The reference voltage v,, applied from C 1 4 to the comparator 12,
This is the comparison output of the comparator 12 in the case of v2 and v3.

That is, the comparator 12 compares the signal from the device under test 13 with the reference voltage v1 every time each strobe pulse is generated, and latches the output.

Here, when the reference voltage of the DAC 14 is 1, the comparator 12
The output of is at L level during the period (to-t1), and at time t
1, and remains in this state until time tn, so that the waveform shown in FIG. 3C can be obtained.

Similarly, when the reference voltage of the DAC 14 is in the state (2), it is at the L level during the period (to-t2) and at the H level during the period (t2-tn), as shown in FIG. 3D.

In addition, when the reference voltage of the DAC is in the state of ■3, the comparator 12
The output of is inverted from L level to H level at time t3, as shown in FIG. 3E.

As is clear from FIG. 3 shown above, if the reference voltage of the DAC 14 changes to V1, V2, V3, the comparator 12
The points at which the outputs of are inverted are t1, t2, respectively. It changes to t3.

Therefore, the screen of the CRT 18 is divided into brightly emitting parts and dark parts, as shown by solid lines a, b, and c in FIG. 4A, respectively.

Here, for example, if a 10-bit DAC 14 is used, a high-resolution reference voltage of 1024 steps can be obtained.

At this time, the display on the screen of the CRT 18 becomes as shown in FIG. 4B, and the waveform representing the operating characteristics of the device under test 13 shown in FIG. 3A can be displayed by the boundaries between bright and dark.

Note that the time axis of the waveform displayed by the luminance difference in FIG. 4B is determined by the slope of the high-speed slope signal shown in FIG. 2C, and is not influenced by the low-speed slope signal shown in FIG. 2A.

Therefore, extremely high-speed signals and ultra-high frequency signals can be observed with high precision like a general sampling oscilloscope.

In the above example, an electrostatic deflection type CRT was used as the display device, but other examples include an accumulation type CRT, an electromagnetic deflection type CRT, and an X-Y pen recorder, an LED matrix, and a liquid crystal display. It is also possible to use any flat (two-dimensional) display device such as a wave, plasma display panel, etc.

Furthermore, in the above example, the outputs of the comparator 12 such as waveforms C, D, and E in Fig. 3 are directly applied to the Z axis of the CRT 1B, but such waveforms can be applied using an appropriate differentiating circuit. By differentiating and adding, the time points t1 and t2 at which the output of the comparator 12 changes
, t3, the electron beam of the CRT 18 is modulated, so that a waveform similar to that of a general oscilloscope or oscilloscope can be displayed.

Furthermore, a monostable multivibrator triggered at these times t1, t2, t3, . . . can also be used and its output applied to the Z-axis.

Here, when an XY pen recorder is used as the display device, the Z-axis signal becomes a pen up-down control signal.

The digital processing circuit 24 shown in FIG. 1 is, for example, a storage circuit using an IC or a magnet, and is configured to receive the digital signal of the DAC 14 (for example, the output of a counter that counts the number of slow slope signals from the time axis circuit) and the comparator 12. The sweep voltage level at the time when the comparison output is inverted is digitally converted and stored.

Thereby, the operating characteristics of the device under test 13 can be stored, and when desired, this stored data can be reproduced and displayed on any of the above-mentioned display devices, and any calculation processing can be performed.

Note that the comparator 12 in FIG. 1 may be, for example, a strobe voltage comparator manufactured by Advanced Microphone Devices.

As can be seen from the above description, the operating characteristics of the device under test 13 can be measured by comparing the displayed waveforms when the device under test 13 is inserted and when the input signal to the terminal 10 is directly observed.

In this case, the input signal can be selected to be the same as the signal that actually operates, and the time axis can be set at a sufficiently high speed by selecting the slope of the high-speed slope signal.
If the AC 14 has a high resolution of 10 bits or more, for example, the measurement accuracy can be as high as 0.1% or more.

Further, the operating characteristic device of the present invention is particularly suitable for measuring the operating characteristics of an S/H circuit.

In other words, in the S/H circuit, when sampling an input signal near the maximum sampling frequency, the amplitude change of the input signal at each sampling point is large.
It is difficult for S/H circuits to faithfully reproduce input signals.

However, according to the device of the present invention, as shown by the broken line in FIG. 1, the S/H circuit 1 is
3 sampling commands are executed, and the sampling period is maintained at a sufficiently high speed, and the successive sampling points are only shifted by a minute time Δt with respect to a specific point of the input signal.

Therefore, since the amount of change in the input signal between successive sampling points is extremely small, it is possible to operate the S/H circuit and dynamically evaluate its operating characteristics even for input signals that exceed the maximum operating frequency. Yes, it has a significant practical effect.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Figs. 2 and 3 are waveform diagrams for explaining the operation of Fig. 1, and Fig. 4 shows an example of waveforms displayed by the device shown in Fig. 1. FIG. In the figure, 12 is a comparator, 13 is a device to be measured, 14 is a digital-to-analog converter, 18 is a display device, and 22 is a pulse generator.

Claims (1)

[Claims] 1. Compare a high-frequency driven device under test to which a periodic input signal is applied, a low-speed ramp signal and a high-speed ramp signal synchronized with the input signal, and sequentially adjust the phase at a constant rate with respect to the input signal. a pulse generator that generates pulses varying in speed to drive the device under test; a high-precision digital-to-analog converter that generates a reference voltage corresponding to the number of generated slow ramp signals; A comparator for comparing the output of the device to be measured, and applying the reference voltage and the low-speed gradient signal to two orthogonal axes respectively, scans the display surface in a scanning line, and converts this scanning into a binary state using the output of the comparator. an operating characteristic measuring device, the operating characteristic measuring device comprising: a display device that selects the input signal frequency to be approximately equal to a maximum driving frequency of the device under test, and displaying the dynamic characteristics of the device under test on the display device. 2. The operating characteristic measuring device according to claim 1, wherein the device under test is a sample-and-hold circuit that performs a sampling operation in synchronization with the output pulse of the pulse generator.