JPS63138281A - Threshold value measuring instrument - Google Patents

Abstract

PURPOSE:To measure the positive/negative-directional input threshold voltage and hysteresis voltage of a device by making a sweep once by generating and applying a sweep voltage which has gradient characteristics to the device. CONSTITUTION:A gradient value is converted 12 by using data from a control circuit 11 and the sweep voltage based upon the gradient value output is generated 13. Then the sweep voltage signal, a start position signal from a setting circuit 14, and a step position signal from a setting circuit 15 are added 16 and supplied to sample holding circuits 17 and 18 and a device 3. Then, the detected value for deciding the operation point of the device 3 from a setting circuit 2 is compared 22 with the output of the device 3 and a control circuit 23 sends holding signals to the circuits 17 and 18 according to the comparison output. The circuits 17 and 18 detect the positive/negative-directional threshold voltages of the device 3.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a threshold measuring device capable of rapidly measuring the threshold voltage of a device having hysteresis.

(b) Conventional technology and problems First, a configuration diagram of the prior art is shown in FIG.

In FIG. 4, 1 is a control circuit, 2 is a power supply circuit, 3 is a device to be tested, and 4 is a voltage measurement circuit.

The output of power supply circuit 2 is supplied to device 3,
The output voltage is measured by a voltage-1 constant circuit 4.

The control circuit 1 controls the output voltage of the power supply circuit 2 and determines the threshold value of the device 3 from the voltage measured by the voltage measurement circuit 4.

Next, an example of a characteristic diagram of the device 3 is shown in FIG.

FIG. 5 shows a case where the device 3 has hysteresis characteristics, the horizontal axis shows the input terminal, and the vertical axis shows the output voltage.

In Figure 5, when the input voltage is increased, the human output characteristic curve suddenly rises at voltage VTII, and when the input terminal is lowered, the input/output characteristic curve suddenly falls at voltage VTL. It becomes like this.

[EVT[I is the positive-going input threshold voltage, and voltage VTL is the negative-going input threshold voltage.

The voltage ΔVT in FIG. 5 is a hysteresis voltage, and the voltage ΔVT
VT=voltage VTII−voltage VTL.

Next, a conventional technique for measuring the device 3 having the characteristics shown in FIG. 5 will be described.

A conventional technique for such cases is a measurement method using an increment function.

The increment function means that the power supply circuit 2 generates a step voltage that increases stepwise as shown in Figure 6, and the control circuit l
It is preferable to add it to device 3 under the control of .

If a step voltage as shown in FIG. 6 is applied to the device 3 and the output voltage of the device 3 is measured by the voltage measuring circuit 4, the value of the voltage VTII can be accurately detected.

In order to measure the voltage Vl, a step voltage that decreases in a stepwise manner, contrary to that shown in FIG. This is called measurement using the decrement function.

However, the voltages VTII, VTL and ΔV of device 3
In order to accurately measure T, the step voltage must be made small.

For example, a step voltage of 1 mV from 1v to 2V is 0.
If it is changed at an interval of 5 ns, it will take 500 m5.

As described above, there is a problem in that it takes a long time when trying to improve accuracy using the measurement method using the increment function.

Next, another conventional technique for measuring the device 3 having the characteristics shown in FIG. 5 will be described.

Another prior art technique includes a measurement method using a binary search function.

The binary search function is a method in which a step voltage as shown in FIG.

FIG. 7(A) shows the input terminal to the device 3, and FIG. 7(B) shows the output voltage from the device 3.

In FIG. 7, voltages V+, V2, and V3 are applied to the device 3 in this order.

In this case, the following relationship should be established.

V3 = (Vl + V2) /2 In other words, in the measurement method using the binary search function shown in Fig. 7, the output voltage is inverted depending on the input voltage, but each time the amplitude of the input voltage is set to a certain condition. The input voltage is brought closer to the threshold value of the device 3 while being controlled by the control circuit 1 so that the input voltage becomes smaller.

FIG. 7 shows an input terminal whose output level changes from "1" to "0" or from "0" to "1" by changing the input voltage between 1v and 4v and determining the output voltage of the device 3. This example shows how to find the value of .

Therefore, the threshold value in FIG. 7 is 2v.

However, in measurement using the binary search function, the voltage v
3 and so on, the threshold value is detected while creating the control circuit 1, which takes time and makes the program for the control circuit 1 complicated.

Furthermore, the M1 determination method using the binary search function is effective for devices with a narrow hysteresis width such as inverters, but when measuring a device 3 with a large hysteresis voltage Δ■ as shown in FIG. If the input voltage falls within the hysteresis width, there is a problem that the threshold cannot be detected accurately.

In other words, according to the measurement method using the increment function, it is possible to measure the device 3 with hysteresis characteristics, but when using the measurement method using the binary search function, it is possible to measure only a device with a narrow width of hysteresis characteristics.

(c1 Purpose of the Invention The present invention provides a measuring device with a configuration different from that of the prior art, which generates an II! pull voltage with a slope characteristic and applies this sweep voltage to the device 3 to
Voltage VTR, VTR and ΔV of device 3 in one sweep
The purpose is to enable measurement of T and to shorten the measurement time.

(d) Examples of the invention First, a block diagram of an embodiment according to the present invention is shown in FIG.

11 in FIG. 1 is a control circuit, 12 is a slope value conversion circuit, and 13
is an integrating circuit, 14 is a start value setting circuit, 15 is a stop value setting circuit, 16 is an addition circuit, 17! : 18 is a sample hold circuit, 21 is a detection level setting circuit, 22 is a comparison circuit, and 23 is a control circuit.

The slope value conversion circuit 12 determines the slope angle of the sweep voltage, and uses a DA converter that converts a digital value into an analog value according to a command from the control circuit 11.

The integrating circuit 13 integrates the output of the slope value converting circuit 12, and produces the fJ main voltage.

The start value setting circuit 14 sets the start position of the sweep voltage.

The stop value setting circuit 15 sets the stop position of the t11 pull voltage.

The start value setting circuit 14 and the stop value setting circuit 15 are
It can be realized with 13A & converter.

The adder circuit 16 adds the sweep output of the integrator circuit 13 and the output of the start value setting circuit 14 to create a start voltage of the sweep voltage, and adds the sweep output of the integrator circuit 13 and the output of the stop value setting circuit 15. , create a stop voltage for the sweep voltage.

The sample and hold circuits 17 and 18 operate according to the output of the comparison circuit 22, and the sample and hold circuit 17 operates according to the output of the comparison circuit 22.
The sample and hold circuit 18 for outputting Tl1m is for detecting the voltage V.

Next, an output waveform diagram of the adder circuit 16 is shown in FIG.

ST in FIG. 2 is a start voltage, and SP is a stop voltage.

The horizontal axis in FIG. 2 shows time, and the vertical axis shows voltage.

Figure 2 (71 indicates the upward right sweep voltage, Figure 2 (a)
indicates a downward-sloping sweep voltage.

The slope conversion circuit 12 is! - Set the inclination angle of the pulling voltage.

FIG. 2(T) shows the sweep voltage changing from upward to right to downward to right.

Incidentally, the slope conversion circuit 12 and the integration circuit 13 can be realized using conventional techniques.

When device 3 has hysteresis characteristics, Figure 2 (T)
When using a sweep voltage of , and the hysteresis width is narrow,
Use Figure 2 (T) or Figure 2 (A).

Next, FIG. 3 shows the input/output voltages of the device 3 when the sweep voltage shown in FIG. 2 is applied to the device 3.

Figure 3 (a) shows the input terminal to device 3, and the time T
The threshold is reached at 1.

Figure 3 (a) shows the output voltage of device 3, and time T1
The voltage changes from "1" to "0".

The detection level setting circuit 21 in FIG. 1 is a DA converter that sets a detection value. The detected value is a value set to determine the operating point of the device 3 on the output side.

The comparison circuit 22 receives the output of the device 3 and the detection level setting circuit 21 as inputs, and outputs No. 43 which activates the sample and hold circuit 17 or 18 when the detected value is exceeded.

The control circuit 23 sends a hold signal from the output of the comparison circuit 22 to the sample and hold circuit 17 or the sample and hold circuit 18.

In other words, the feature of the threshold measuring device shown in FIG. 1 is that by continuously changing the voltage or current applied to the device 3, interaction with the control circuit 11 is kept to a minimum and the measurement time is shortened. be.

The actual operation can be summarized as follows.

(1) Slope data, detection data, etc. from the control circuit 11 are transferred to the slope conversion circuit 12 and the detection level setting circuit, respectively.

(a) At the start of measurement, the voltage shown in FIG. 2 that continuously increases or decreases from the slope conversion circuit 12 is applied to the device 3.

(c) When the input voltage changes and the output of the device 3 changes, this change becomes the input terminal of the comparison circuit 22, and this input voltage and the output of the detection level setting circuit 21 are compared in the comparison circuit 22. , and when they match, a hold signal is transmitted to the sample and hold circuits 17 and 18.

(1) Sample and hold circuit 17 that receives a hold signal
．． 18 maintains a value proportional to the tilt output, and uses that value as the measured value.

(In the operations of 11(7) to (1), the slope output is continuously increased, the output change of the device 3 is continued to be detected, the slope output is automatically continuously decreased, and the slope output is automatically decreased again, and the slope output is continuously detected. If the output change is detected, the measured value will be the voltage VTH and voltage VT.
The voltage becomes L, and the voltage ΔV is calculated from the value of voltage VTII - voltage VTL.
T is determined, and the voltages VTR, VTL, Δ
Finish the VT measurement.

(e) Effects of the Invention According to this invention, the voltage or current applied to the device can be continuously changed during one test, so the test time per test can be measured using the increment function. It can be shorter than measurements using a binary search function or a binary search function.

Further, the threshold measuring device according to the present invention can be installed alongside a conventional device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment according to the present invention, FIG. 2 is a diagram of the output waveform of the adder circuit 16, FIG. 3 is a diagram of the input voltage waveform applied to the device 3 and the output waveform of the device 3, and FIG. FIG. 5 is a configuration diagram of a measuring device according to the prior art. FIG. 5 is an example of a characteristic waveform diagram of the device 3. FIG. 6 is a measurement waveform diagram using the increment function, and FIG. 7 is a measurement waveform diagram using the pinary surge function. l... Control circuit, 2... Power supply circuit, 3
...device, 4...voltage measurement circuit,
11... Control circuit, 12... Slope conversion circuit, 13... Integrating circuit, 14... Start value setting circuit, 15...... Stop value setting circuit, 18... Addition circuit, 17... Sample hold circuit, 18... Sample hold circuit, 21... Detection level setting circuit, 22・・・
... Comparison circuit, 23 ... Control circuit. Agent Patent Attorney Kin Omata 4 Figure 1 Detection level setting circuit Comparison circuit Control circuit Figure 2 (A) (B) (T) 3
Figure Time 4 Figure 5 vTL VTH Figure 6 □ Time □ Time □ Time December 25, 1985 1. Display of incident Patent application No. 285032 of 1985 2. Title of invention Threshold measuring device 3 , Relationship with the case of the person making the amendment Patent Applicant Address: Inside Ando Electric Co., Ltd., 4-19-7 Kamata, Ota-ku, Tokyo. Name (8402) Patent Attorney Kinji Omata, °“Pa i5, Date of Amendment Order Voluntary i
'6. Number of inventions increased by amendment 07. Subject of amendment "Detailed description of the invention" column of the specification. 8. Contents of amendment (1) rO, 5nsJ on page 4, line 14 of the specification is r
Correct it to O, 5m5J. (2) rVTHJ on page 7, line 5 of the specification is rVTL
Correct with J. (3) Correct "Slope value conversion port" in the 10th line of page 7 of the specification to "Slope conversion port". (4) “Slope value conversion circuit” on page 7, line 16 of the specification
is corrected as a "slope conversion circuit". (5) “Slope value conversion circuit” on page 7, line 20 of the specification
is corrected as a "slope conversion circuit". (G) On page 11, line 2 of the specification, “As the changes continue,
” is corrected to ``As it changes,''.

Claims (1)

[Claims] 1. A slope conversion circuit (12) that converts a slope value based on data from a control circuit (11); and an integration circuit (13) that receives the output of the slope conversion circuit (12) and generates a sweep voltage. ), a start value setting circuit (14) that sets the start position of the sweep voltage, a stop value setting circuit (15) that sets the stop position of the sweep voltage, and the output and start value of the integration circuit (13). Setting circuit (1
4) and the output of the stop value setting circuit (15) as inputs, and sample and hold circuits (17) and (18) that receive the output of the adder circuit (16) as inputs, and the detected value. A detection level setting circuit (21) that sets the detection level setting circuit (21), the output of the detection level setting circuit (21), and the output of the addition circuit (16) are added to the device (3), and the output from the device (3) is input. A comparison circuit (22) and a comparison circuit (22)
) Sample and hold circuits (17), (18) from the output of
A threshold measuring device comprising: a control circuit (23) that outputs a hold signal.