JP2015040843A - Signal generator, signal generation method, testing device, and testing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compensate distortion of a signal corresponding to frequency characteristics of a circuit connected to a latter part of an integration circuit.SOLUTION: There is provided a signal generator which generates a signal corresponding to an input signal. The signal generator includes an integration capacitor and a series resistance provided in series, includes an integration circuit for integrating the input signal, and in which at least one of capacity of the integration capacitor and an ohmic value of the series resistance is variable. A band limiting circuit connected to a latter part of the integration circuit and an adjustment part for adjusting at least one of the capacity of the integration capacitor and the ohmic value of the series resistance based on time constant of the band limiting circuit can be further included.

Description

  The present invention relates to a signal generator, a signal generation method, a test apparatus, and a test method.

2. Description of the Related Art Conventionally, in a waveform generator that generates a signal, a circuit that adds a square wave to a signal is known to compensate for waveform distortion in a low-pass filter for noise removal (see, for example, Patent Document 1).
[Prior art documents]
Patent Document 1 Japanese Patent Laid-Open No. 2006-337139 Patent Document 2 Japanese Utility Model Laid-Open No. 03-12564

  However, the conventional waveform generator has to include a circuit for generating a square wave and a circuit for adding the square wave, which increases the circuit scale.

  In a first aspect of the present invention, a signal generator that generates a signal according to an input signal, includes an integrating capacitor and a series resistor provided in series, and includes an integrating circuit that integrates the input signal, and integrating Provided is a signal generator in which at least one of a capacitance of a capacitor and a resistance value of a series resistor is variable, and a signal generation method using the signal generator.

  In a second aspect of the present invention, a signal generator for generating a signal corresponding to an input signal, comprising: an integration circuit to which the input signal is input; and a band limiting circuit connected to a subsequent stage of the integration circuit. The integration circuit is provided in series and includes an integration capacitor and a series resistor to which an input signal is input, and a time constant corresponding to the product of the capacitance of the integration capacitor and the resistance value of the resistor is equal to the time constant of the band limiting circuit. A signal generator and a signal generation method using the signal generator are provided.

  According to a third aspect of the present invention, there is provided a test apparatus for testing a device under test, which generates a signal corresponding to an input signal and inputs the signal to the device under test. And a test apparatus including a determination unit that determines the quality of the device under test based on the operation of the device under test, and a test method using the test device.

  It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

It is a figure which shows the structural example of the signal generator 100 which concerns on embodiment of this invention. 3 is a diagram illustrating an example of frequency characteristics of an integrating circuit 10 and a band limiting circuit 30. FIG. It is a figure which shows an example of the waveform of the constant current signal Iin, the integration signal V1, and the output signal V2. FIG. 5 is a diagram illustrating another configuration example of the signal generator 100. FIG. 5 is a diagram illustrating another configuration example of the signal generator 100. 3 is a diagram illustrating a configuration example of a compensation circuit 40. FIG. 4 is a diagram illustrating an example of frequency characteristics of an integrating circuit 10, a compensating circuit 40, and a band limiting circuit 30. FIG. 6 is a diagram illustrating another configuration example of the compensation circuit 40. FIG. 6 is a diagram illustrating another configuration example of the compensation circuit 40. FIG. 6 is a diagram illustrating another configuration example of the band limiting circuit 30 and the compensation circuit 40. FIG. It is a figure which shows the structural example of the test apparatus 200 which concerns on embodiment of this invention.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

  FIG. 1 is a diagram illustrating a configuration example of a signal generator 100 according to an embodiment of the present invention. The signal generator 100 generates an output signal corresponding to the input signal. The signal generator 100 of this example includes a signal input unit 22, an integration circuit 10, an adjustment unit 20, and a band limiting circuit 30.

  The signal input unit 22 generates an input signal. The signal input unit 22 of this example has a constant current source. The signal input unit 22 in this example generates a pulsed constant current signal Iin by controlling on and off of the constant current source. Note that the signal input unit 22 may be provided outside the signal generator 100.

  The integration circuit 10 includes an integration capacitor 14 and a series resistor 16 provided in series, and outputs an integration signal V1 obtained by integrating the input signal. The integration circuit 10 of this example generates an integration signal V1 having a ramp waveform. The ramp waveform is a waveform in which the intensity increases or decreases with a substantially constant slope. The integration circuit 10 of this example includes an integration capacitor 14, a series resistor 16, and a differential amplifier 12. The integrating capacitor 14 and the series resistor 16 connected in series are provided between the negative side input terminal and the output terminal of the differential amplifier 12. A reference potential such as a ground potential is applied to the positive input terminal of the differential amplifier 12.

  When there is no series resistor 16, the frequency characteristic of the integrating circuit 10 shows a characteristic that the gain decreases according to the frequency. On the other hand, the integration circuit 10 of this example includes a series resistor 16 connected in series to the integration capacitor 14. For this reason, the frequency characteristic of the integrating circuit 10 shows a substantially constant gain on the higher frequency side than the frequency corresponding to the product (time constant) of the capacitance of the integrating capacitor 14 and the resistance value of the series resistor 16. In other words, the gain in the high frequency band can be increased by providing the series resistor 16.

  In the integration circuit 10 of this example, at least one of the capacitance of the integration capacitor 14 and the resistance value of the series resistor 16 is variable. In FIG. 1, both the integrating capacitor 14 and the series resistor 16 are shown as variable elements. For example, the integrating capacitor 14 includes a plurality of capacitors provided in parallel and a switch for switching whether or not each capacitor is connected to the positive input terminal or the output terminal of the differential amplifier 12. The series resistor 16 includes a plurality of resistors provided in series and a switch for switching whether or not to bypass by connecting both ends of each resistor. By controlling these switches, the capacitance or the resistance value can be controlled.

  The band limiting circuit 30 is connected to the subsequent stage of the integration circuit 10 and receives the integration signal V1 output from the integration circuit 10. A relay circuit such as an attenuator or an offset application circuit may be included between the integrating circuit 10 and the band limiting circuit 30. The band limiting circuit 30 outputs an output signal V2 in which the band of the integration signal V1 is limited.

  The band limiting circuit 30 of this example includes a differential amplifier 32, a resistor 34, a limiting resistor 36, and a limiting capacitor 38. The integration signal V <b> 1 is input to the negative input terminal of the differential amplifier 32 via the resistor 34. A reference potential such as a ground potential is applied to the positive input terminal of the differential amplifier 32.

  The limiting resistor 36 is provided between the negative input terminal and the output terminal of the differential amplifier 32. The limiting capacitor 38 is provided in parallel with the limiting resistor 36 between the negative input terminal and the output terminal of the differential amplifier 32. With such a configuration, the band limiting circuit 30 of this example functions as a low-pass filter. Thereby, the high frequency noise contained in the integration signal V1 can be removed. However, the high-frequency component of the integration signal V1 includes the original signal component. For this reason, passing through the band limiting circuit 30 causes distortion in the integrated signal V1.

  The adjustment unit 20 controls at least one of the capacitance of the integration capacitor 14 and the resistance value of the series resistor 16 in the integration circuit 10 in order to compensate in advance for distortion of the integration signal V1 caused by passing through the band limiting circuit 30. More specifically, the adjusting unit 20 controls at least one of the capacitance of the integrating capacitor 14 and the resistance value of the series resistor 16 so that the time constant of the integrating circuit 10 and the time constant of the band limiting circuit 30 match. To do. That is, the adjustment unit 20 makes the product of the capacitance of the integrating capacitor 14 and the resistance value of the series resistor 16 equal to the product of the capacitance of the limiting capacitor 38 and the resistance value of the limiting resistor 36.

  By such control, the high frequency band in which the gain is suppressed in the band limiting circuit 30 and the high frequency band in which the gain is increased in the integrating circuit 10 can be substantially matched. For this reason, the high frequency signal component whose gain is limited in the band limiting circuit 30 can be increased in the integrating circuit 10 in advance. Thus, a desired waveform can be output while removing high-frequency noise in the band limiting circuit 30.

  In addition, the case where the time constants are “matched” includes not only the case where the time constants are exactly matched, but also the case where the time constants are substantially matched so that the distortion of the integrated signal V1 can be compensated to be within the allowable range. In this example, if the ratio between the time constant of the integrating circuit 10 and the time constant of the band limiting circuit 30 is within the range of 90% to 110%, it may be considered substantially coincident.

  The adjusting unit 20 of this example receives circuit information indicating the time constant of the band limiting circuit 30 connected to the subsequent stage of the integrating circuit 10, and based on the circuit information, the capacitance of the integrating capacitor 14 and the resistance value of the series resistor 16 Adjust. The circuit information may include a time constant value and may include identification information associated with the time constant of the band limiting circuit 30. The adjustment unit 20 may receive the circuit information from the band limiting circuit 30 or may receive it from a user of the signal generator 100 or the like.

  The band limiting circuit 30 may be replaceable in the signal generator 100, and the time constant may be changeable. The band limiting circuit 30 may be an external circuit connected to the signal generator 100. Since the characteristic values of the integrating capacitor 14 and the series resistor 16 are variable, the time constant of the integrating circuit 10 can be adjusted according to the time constant of the band limiting circuit 30 connected in the subsequent stage. Further, the configuration of the band limiting circuit 30 is not limited to the configuration shown in FIG. The band limiting circuit 30 may include a limiting capacitor 38 and a limiting resistor 36 provided in series. The adjustment unit 20 may be provided outside the signal generator 100.

  FIG. 2 is a diagram illustrating an example of frequency characteristics of the integrating circuit 10 and the band limiting circuit 30. In FIG. In FIG. 2, the horizontal axis represents frequency and the vertical axis represents gain. The capacitance of the integrating capacitor 14 is Cf, the resistance value of the series resistor 16 is Rf, the capacitance of the limiting capacitor 38 is CL, and the resistance value of the limiting resistor 36 is RL. As described above, the frequency characteristic of the integrating circuit 10 is such that the gain decreases according to the frequency at a frequency lower than the frequency 1 / 2πRfCf corresponding to the time constant, and becomes a substantially constant gain at the frequency higher than the frequency. In FIG. 2, the frequency characteristic of the integrating circuit 10 when there is no series resistor 16 is indicated by a broken line.

  Further, the band limiting circuit 30 has a substantially constant gain on the lower frequency side than the frequency 1 / 2πRLCL corresponding to the time constant, and the gain decreases on the higher frequency side from the frequency according to the frequency. The adjusting unit 20 matches the time constants of the integrating circuit 10 and the band limiting circuit 30. Thereby, the distortion of the integration signal V1 by the band limiting circuit 30 can be compensated. Note that the slope of the frequency characteristic of the high-frequency band limiting circuit 30 preferably coincides with the slope of the high-frequency side frequency characteristic of the integrating circuit 10 without the series resistor 16.

  FIG. 3 is a diagram illustrating an example of waveforms of the constant current signal Iin, the integration signal V1, and the output signal V2. In FIG. 3, the horizontal axis represents time, and the vertical axis represents signal intensity. The signal waveform when there is no series resistor 16 is indicated by a broken line.

  The signal input unit 22 of this example generates a pulsed constant current signal Iin. The integration circuit 10 outputs an integration signal V1 obtained by integrating the constant current signal Iin. The band limiting circuit 30 outputs an output signal V2 from which the high frequency component of the integrated signal V1 has been removed.

  When the integration circuit 10 does not have the series resistor 16, the waveform of the integration signal V1 output from the integration circuit 10 is a ramp waveform. However, since the gain of the high frequency component is limited by the band limiting circuit 30, the waveform of the output signal V2 output from the band limiting circuit 30 is distorted with respect to the ramp waveform.

  On the other hand, since the integration circuit 10 has the series resistor 16, the high frequency component of the integration signal V1 output from the integration circuit 10 increases. For this reason, the waveform of the output signal V2 through which the integration signal V1 has passed through the band limiting circuit 30 is a ramp waveform. Therefore, the signal generator 100 can accurately form the waveform of the output signal V2 over the entire band while reducing high-frequency noise in the output signal V2. Note that the waveform of the output signal V2 of the signal generator 100 is not limited to the ramp waveform.

  FIG. 4 is a diagram illustrating another configuration example of the signal generator 100. The signal generator 100 of this example does not have the adjustment unit 20. The band limiting circuit 30 is fixed with respect to the integrating circuit 10, and the time constant is also fixed. The characteristic values of the integrating capacitor 14 and the series resistor 16 are also fixed. Other configurations are the same as those of the signal generator 100 described in FIGS. 1 to 3.

  In the signal generator 100 of this example, the characteristic values of the integrating capacitor 14 and the series resistor 16 are designed in advance so that the time constant of the integrating circuit 10 matches the time constant of the band limiting circuit 30. Even with such a configuration, the waveform of the output signal V2 can be accurately formed over the entire band while reducing high-frequency noise in the output signal V2.

  FIG. 5 is a diagram illustrating another configuration example of the signal generator 100. The signal generator 100 of this example further includes a compensation circuit 40 in addition to the configuration of any one of the signal generators 100 described in FIGS. FIG. 5 shows an example in which a compensation circuit 40 is added to the configuration of the signal generator 100 shown in FIG. 5 further includes an equivalent circuit (a series circuit of an equivalent resistor 18 and an equivalent capacitor 19) showing dielectric absorption of the integration capacitor 14. The integration circuit 10 shown in FIG. In general, an equivalent circuit of dielectric absorption in a capacitor is represented by a circuit in which a series circuit of a resistor and a capacitor is connected in parallel with the original capacitor.

  When the dielectric absorption of the integration capacitor 14 cannot be ignored, the integration signal V1 output from the integration circuit 10 is distorted by dielectric absorption. Specifically, due to the equivalent resistor 18 and the equivalent capacitor 19, the frequency characteristic of the integrating circuit 10 is such that the gain of the low frequency component is reduced (or the high frequency component of the high frequency component) compared to the frequency characteristic when the dielectric absorption is not considered. Gain increases). The fluctuation of the gain is determined by the capacitance ratio of the integrating capacitor 14 and the equivalent capacitor 19.

  The compensation circuit 40 inputs the integration signal V1 compensated for distortion caused by the dielectric absorption to the band limiting circuit 30. The compensation circuit 40 of this example includes an RC series circuit whose time constant is equal to the time constant of an equivalent circuit of dielectric absorption in the integrating capacitor 14. The compensation circuit 40 adds and subtracts the compensation signal obtained by limiting the band of the integration signal V1 with the RC series circuit and the integration signal V1, and outputs the result.

  FIG. 6 is a diagram illustrating a configuration example of the compensation circuit 40. The compensation circuit 40 of this example includes a first voltage dividing resistor 44, an RC series circuit 42, and a voltage follower circuit 50. The RC series circuit 42 includes a second voltage dividing resistor 46 and a compensation capacitor 48. The first voltage dividing resistor 44 is provided between the output terminal of the integrating circuit 10 and the reference potential. The second voltage dividing resistor 46 is provided in series with the first voltage dividing resistor 44 between the first voltage dividing resistor 44 and the reference potential. The resistance value of the second voltage dividing resistor 46 may be larger than the resistance value of the first voltage dividing resistor 44. The compensation capacitor 48 is provided in series with the second voltage dividing resistor 46 between the first voltage dividing resistor 44 and the reference potential. In the example of FIG. 6, the second voltage dividing resistor 46 is connected to the first voltage dividing resistor 44, and the compensation capacitor 48 is provided between the second voltage dividing resistor 46 and the reference potential. A second voltage dividing resistor 46 connected to the first voltage dividing resistor 44 may be provided between the compensation capacitor 48 and the reference potential. The voltage follower circuit 50 receives a signal at a contact point of the first voltage dividing resistor 44 and the RC series circuit 42 (in this example, a contact point of the first voltage dividing resistor 44 and the second voltage dividing resistor 46), and according to the signal Output a signal.

  Since the second voltage dividing resistor 46 and the compensation capacitor 48 are provided in series between the signal line and the reference potential, the RC series circuit of this example functions as a low-pass filter. The signal output from the RC series circuit 42 (in this example, the signal at the contact point of the first voltage dividing resistor 44 and the second voltage dividing resistor 46) includes a compensation signal in which the band of the integration signal V1 is limited by the low-pass filter, The signal V1 is a signal obtained by adding the specific gravity according to the resistance ratio of the first voltage dividing resistor 44 and the second voltage dividing resistor 46.

Here, the resistance ratio of the first voltage dividing resistor 44 and the second voltage dividing resistor 46 is equal to the ratio of the dielectric absorption equivalent capacitance (that is, the capacitance of the equivalent capacitor 19) and the capacitance of the integrating capacitor 14. That is, when the resistance values of the first voltage dividing resistor 44 and the second voltage dividing resistor 46 are R1 and R2, and the capacitance of the integrating capacitor 14 and the capacitance of the equivalent capacitor 19 are Cf and Cd, the following relationship is established.
R1: R2 = Cd: Cf Formula (1)
Further, since the time constant of the dielectric absorption equivalent circuit and the time constant of the RC series circuit 42 are matched, the following relationship is established. However, the resistance value of the equivalent resistance is Rd, and the capacitance of the compensation capacitor 48 is C1.
Rd × Cd = R2 × C1 Formula (2)

  As a result, the compensation circuit 40 adds and subtracts the integration signal V1 and the compensation signal according to the capacitance ratio of the integration capacitor 14 and the equivalent capacitor 19. Therefore, the dielectric absorption can compensate for the low frequency component whose gain is relatively small with respect to the gain of the high frequency component in accordance with the capacitance ratio of the integrating capacitor 14 and the equivalent capacitor 19.

  Note that the ratio “equal” includes not only the case where the ratio is exactly the same but also the case where the ratio is substantially equal to the extent that the distortion due to the dielectric absorption can be compensated until it falls within the allowable range. In this example, if the ratio of the resistance values is within the range of 90% to 110% of the ratio of the capacitance values, it may be considered substantially equal.

The capacitance of the compensation capacitor 48 may be a capacitance obtained by multiplying the capacitance of the equivalent capacitor 19 by a predetermined coefficient A greater than 1. In this case, as is apparent from the equation (2), the second voltage dividing resistor 46 has a resistance value obtained by dividing the resistance value of the equivalent resistor 18 by the coefficient. Further, as apparent from the equation (1), the first voltage dividing resistor 44 is a resistance obtained by dividing the product of the resistance value of the equivalent resistor 18 and the capacitance of the equivalent capacitor 19 by the product of the capacitance of the integrating capacitor 14 and the coefficient. Has a value. That is, it has the following relationship.
C1 = A × Cd
R2 = Rd / A
R1 = (Cd × Rd) / (Cf × A)
Thereby, the resistance value of each voltage dividing resistor can be reduced. The value of the coefficient A is about 10 times, for example.

  FIG. 7 is a diagram illustrating an example of frequency characteristics of the integration circuit 10, the compensation circuit 40, and the band limiting circuit 30. The frequency characteristic of the band limiting circuit 30 is the same as the frequency characteristic shown in FIG. Due to the dielectric absorption of the integrating capacitor 14, the frequency characteristic of the integrating circuit 10 of this example is different from the frequency characteristic shown in FIG.

  As described above, the frequency characteristic of the integration circuit 10 is such that the gain of the low frequency component decreases (or the gain of the high frequency component increases) with respect to the frequency characteristic when the dielectric absorption is not considered. Specifically, the frequency characteristic on the lower frequency side than the predetermined frequency f1 (where f1 = 1 / (2πCdRd)) and the frequency characteristic on the higher frequency side than the predetermined frequency f2 are not linear, and Frequency characteristics are relatively low. The frequency f2 is a frequency at which the impedance of the equivalent circuit for dielectric absorption becomes very large and can be ignored with respect to the impedance of the integrating capacitor 14. Further, the gain of the integrating circuit 10 is substantially constant in the interval from the frequency f1 to f2.

  On the other hand, in the frequency characteristic of the compensation circuit 40, the impedance of the compensation capacitor 48 is large on the lower frequency side than the frequency f1, and almost no current flows through the RC series circuit 42. Therefore, the gain is approximately 1. In the section from the frequency f1 to f2, the low-pass characteristic in which the gain gradually decreases is shown. On the higher frequency side than the frequency f2, the impedance of the compensation capacitor 48 is much smaller than the resistance value of the second voltage dividing resistor 46, and can be almost ignored. For this reason, the integration signal V1 output from the integration circuit 10 is divided by the resistance ratio of the voltage dividing resistor.

  By using the compensation circuit 40 having such frequency characteristics, it is possible to compensate for the gap between the frequency characteristics on the low frequency side and the high frequency side in the integration circuit 10 caused by dielectric absorption. Similarly to the example shown in FIG. 2, by providing the series resistor 16, a high-frequency signal component removed by the band limiting circuit 30 can be compensated in advance by the integrating circuit 10.

  In the configuration in which the compensation circuit 40 is added to the signal generator 100 in which the characteristic values of the integrating capacitor 14 and the series resistor 16 shown in FIG. 1 are variable, at least the characteristic value of each element in the RC series circuit 42 is used. Preferably one is variable. The adjusting unit 20 may adjust the characteristic value of each element in the RC series circuit 42 according to the characteristic value of the integrating capacitor 14 and the series resistor 16 in the integrating circuit 10.

  FIG. 8 is a diagram illustrating another configuration example of the compensation circuit 40. The compensation circuit 40 of this example has a configuration in which the amplifier circuit 60 is provided in place of the voltage follower circuit 50 in the compensation circuit 40 shown in FIG. The amplifier circuit 60 amplifies and outputs a signal at a contact point of the first voltage dividing resistor 44 and the RC series circuit 42 (in this example, a contact point of the first voltage dividing resistor 44 and the second voltage dividing resistor 46).

  The amplifier circuit 60 includes an amplification resistor 64, an amplification resistor 66, and a differential amplifier 62. The amplification resistor 64 is connected between the contact of the first voltage dividing resistor 44 and the RC series circuit 42 and the negative side input terminal of the differential amplifier 62. The amplification resistor 66 is connected between the negative input terminal of the differential amplifier 62 and the output terminal. The amplifier circuit 60 amplifies the signal at an amplification factor according to the resistance ratio of the amplification resistor. The resistance value of the amplification resistor 64 is preferably sufficiently larger than the resistance value of the second voltage dividing resistor 46 so as not to affect the addition ratio between the integration signal V1 and the compensation signal. With such a configuration, the integrated signal compensated for distortion can be amplified and output.

  FIG. 9 is a diagram illustrating another configuration example of the compensation circuit 40. The compensation circuit 40 of this example includes an RC series circuit 42, a second voltage dividing resistor 46, resistors 70, 72, 74, and 76, a differential amplifier 68, and a buffer 78.

  The resistor 70 is connected between the output terminal of the integrating circuit 10 and the negative input terminal of the differential amplifier 68. The resistor 72 is connected between the negative side input terminal and the output terminal of the differential amplifier 68. The resistance values of the resistor 70 and the resistor 72 are the same.

  The RC series circuit 42 of this example includes a compensation capacitor 48 and a first voltage dividing resistor 44. The compensation capacitor 48 is provided between the line connecting the output terminal of the integrating circuit 10 and the resistor 70 and the reference potential. The first voltage dividing resistor 44 is provided in series with the compensation capacitor 48 between the output terminal of the integrating circuit 10 and the reference potential. The second voltage dividing resistor 46 is provided between the first voltage dividing resistor 44 and the reference potential. In the example of FIG. 9, the compensation capacitor 48 is connected to the output terminal of the integrating circuit 10, and the first voltage dividing resistor 44 is provided between the compensation capacitor 48 and the second voltage dividing resistor 46. The voltage resistor 44 may be connected to the output terminal of the integrating circuit 10, and the compensation capacitor 48 may be provided between the first voltage dividing resistor 44 and the second voltage dividing resistor 46.

The RC series circuit 42 of this example functions as a high-pass filter that passes the high-frequency component of the integration signal V1 output from the integration circuit 10. In this example, the signal that has passed through the RC series circuit 42 is a compensation signal. However, the RC series circuit 42 passes the high-frequency component with a gain corresponding to the resistance ratio of the first voltage dividing resistor 44 and the second voltage dividing resistor 46. The characteristic values of the compensation capacitor 48, the first voltage dividing resistor 44, and the second voltage dividing resistor 46 are as follows.
C1 = A × Cd
R1 = Rd / A
R2 = (Cd × Rd) / (Cf × A)
Also in this example, the time constant of the RC series circuit 42 matches the time constant of the equivalent circuit of dielectric absorption. That is, C1 × R1 = Cd × Rd.

  The resistor 74 includes a contact point between the RC series circuit 42 and the second voltage dividing resistor 46 (in this example, a contact point between the first voltage dividing resistor 44 and the second voltage dividing resistor 46), and a positive input terminal of the differential amplifier 68. Between. The differential amplifier 68 functions as an addition / subtraction circuit that adds a signal obtained by inverting the integration signal V1 and the compensation signal output from the RC series circuit 42. As a result, as shown in FIG. 7, the high-frequency component whose gain is relatively increased in the integration signal V <b> 1 can be reduced in the compensation circuit 40.

  Such a configuration can also compensate for distortion due to dielectric absorption. That is, in the configuration shown in FIG. 6, the distortion is compensated by adding the output of the RC series circuit 42 that functions as a low-pass filter to the integration signal V1, but in the configuration shown in FIG. 9, the output functions as a high-pass filter. The distortion was compensated by subtracting the output of the RC series circuit 42 to be integrated from the integrated signal V1. Either method can compensate for distortion due to dielectric absorption.

  The buffer 78 detects a reference potential (for example, ground potential GND) of a circuit connected to the subsequent stage of the compensation circuit 40. The buffer 78 controls the reference level of the positive input terminal of the differential amplifier 68 according to the detected reference potential. In this example, the output terminal of the buffer 78 is connected to the positive input terminal of the differential amplifier 68 via the resistor 76. The resistance values of the resistor 74 and the resistor 76 are equal. As a result, the reference level of the signal output from the compensation circuit 40 can correspond to the reference potential in the subsequent circuit.

  FIG. 10 is a diagram illustrating another configuration example of the band limiting circuit 30 and the compensation circuit 40. In FIG. 10, the integration circuit 10 and the signal input unit 22 are shown together. In this example, the compensation circuit 40 is provided after the band limiting circuit 30. The integration circuit 10 of this example shows an equivalent circuit of dielectric absorption in more detail. Specifically, the equivalent circuit has a plurality of sets of equivalent resistors 18 and equivalent capacitors 19 in parallel. FIG. 10 shows two such sets.

  The band limiting circuit 30 of this example includes a limiting resistor 36, a limiting capacitor 38, and a voltage follower circuit 39. The limiting resistor 36 is provided between the output terminal of the integrating circuit 10 and the input terminal of the voltage follower circuit 39. The limiting capacitor 38 is provided between the wiring connecting the limiting resistor 36 and the voltage follower circuit 39 and the reference potential. The configuration of the band limiting circuit 30 is not limited to the configuration shown in FIG.

  The compensation circuit 40 of this example includes a plurality of RC series circuits 42, a differential amplifier 82, and a resistor 80. In FIG. 10, two RC series circuits 42 are shown. Each RC series circuit 42 corresponds to any set of the equivalent capacitor 19 and the equivalent resistance 18 in the equivalent circuit of dielectric absorption.

  If the equivalent circuit of dielectric absorption can be approximated by a set of equivalent capacitor 19 and equivalent resistor 18, the compensation circuit 40 of this example may also have only one RC series circuit 42. Similarly, each compensation circuit 40 shown in FIGS. 6 to 9 has a plurality of RC series circuits 42 when the equivalent circuit of dielectric absorption is approximated by a plurality of sets of equivalent capacitors 19 and equivalent resistors 18. It's okay.

  The RC series circuit 42 of this example includes a compensation capacitor 48 and a compensation resistor 49. The compensation capacitor 48 is provided between the output terminal of the band limiting circuit 30 and the negative side input terminal of the differential amplifier 82. The compensation resistor 49 is provided between the compensation capacitor 48 and the negative side input terminal of the differential amplifier 82. Each RC series circuit 42 is provided in parallel between the output terminal of the band limiting circuit 30 and the negative input terminal of the differential amplifier 82.

  The characteristic value of each element in the RC series circuit 42 is determined according to the characteristic value of the corresponding equivalent capacitor 19 and equivalent resistor 18 in the same manner as the characteristic value of each element in the RC series circuit 42 shown in FIG. The compensation resistor 49 corresponds to the first voltage dividing resistor 44. Each RC series circuit 42 passes the high frequency component of the integration signal V1.

The resistor 80 is provided between the negative side input terminal and the output terminal of the differential amplifier 82. The resistance value R of the resistor 80 is given by the following equation. However, the capacitance of the equivalent capacitor 19-1 is Cd1, the resistance value of the equivalent resistor 18-1 is Rd1, the capacitance of the equivalent capacitor 19-2 is Cd2, and the resistance value of the equivalent resistor 18-2 is Rd2.
R = ((Cd1 + Cd2) / Cf) × ((Rd1 × Rd2) / (Rd1 + Rd2)) / A

  A reference potential (for example, ground potential GND) of a circuit connected to the subsequent stage of the compensation circuit 40 is input to the positive input terminal of the differential amplifier 82. The differential amplifier 82 amplifies the compensation signal output from the RC series circuit 42 with an amplification factor corresponding to the resistance value of the resistor 80 and the ground potential GND as a reference level. The output terminal of the differential amplifier 82 is connected to the positive input terminal of the differential amplifier 12.

  The compensation circuit 40 of this example feeds back a signal corresponding to the high frequency component in the integrated signal V1 to the differential amplifier 12. Such a configuration can also compensate for distortion in the integration signal V1.

  FIG. 11 is a diagram illustrating a configuration example of the test apparatus 200 according to the embodiment of the present invention. The test apparatus 200 of this example tests a device under test 300 such as an AD converter or a semiconductor circuit. The test apparatus 200 includes a signal generator 100 and a determination unit 110.

  The signal generator 100 is the same as any one of the signal generators 100 described in FIGS. The signal generator 100 generates a signal to be input to the device under test 300. For example, when the device under test 300 is an AD converter, the signal generator 100 generates a ramp wave.

  The determination unit 110 measures the operation of the device under test 300 to which the signal is input from the signal generator 100. The determination unit 110 may measure a signal output from the device under test 300, or may measure fluctuations in a power supply voltage, a power supply current, and the like applied to the device under test 300. When the device under test 300 is an AD converter, the determination unit 110 detects a digital value obtained by sequentially converting each level of the ramp wave by the AD converter.

  The determination unit 110 determines pass / fail of the device under test 300 based on the measurement result. The determination unit 110 may determine pass / fail of the device under test 300 based on whether the measurement result matches a predetermined expected value. Since the test apparatus 200 of this example can input a signal with less distortion with respect to a desired waveform to the device under test 300, the device under test 300 can be accurately tested.

  The test apparatus 200 may include a performance board on which the device under test 300 is placed and a test board on which a test circuit is provided. The signal generator 100 may be all provided on the test board, the band limiting circuit 30 may be provided on the performance board, and the integration circuit 10 may be provided on the test board. Even if the band limiting circuit 30 connected to the integrating circuit 10 is changed by replacing the performance board, the signal generator 100 having the adjusting unit 20 shown in FIG. Thus, the integrating circuit 10 can be adjusted.

  The signal generator 100 can be used for various purposes other than the test of the device under test 300. For example, since the signal generator 100 can generate a highly accurate ramp wave, it is suitable for various applications using the ramp wave. As an example, by detecting the level of the ramp wave at two input timings and measuring the level difference, it is possible to accurately detect the timing time difference.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  The order of execution of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown in the claims, the description, and the drawings is particularly “before” or “prior to”. It should be noted that the output can be realized in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the description, and the drawings, even if it is described using “first”, “next”, etc. for convenience, it means that it is essential to carry out in this order. It is not a thing.

DESCRIPTION OF SYMBOLS 10 ... Integration circuit, 12 ... Differential amplifier, 14 ... Integration capacitor, 16 ... Series resistance, 18 ... Equivalent resistance, 19 ... Equivalent capacitor, 20 ... Adjustment part, DESCRIPTION OF SYMBOLS 22 ... Signal input part, 30 ... Band-limiting circuit, 32 ... Differential amplifier, 34 ... Resistor, 36 ... Limiting resistor, 38 ... Limiting capacitor, 39 ... Voltage follower Circuit: 40: Compensation circuit: 42: RC series circuit, 44: First voltage dividing resistor, 46: Second voltage dividing resistor, 48: Compensation capacitor, 49: Compensation resistor 50 ... Voltage follower circuit, 60 ... Amplifier circuit, 62 ... Differential amplifier, 64, 66 ... Amplification resistor, 68 ... Differential amplifier, 70, 72, 74, 76,.・ Resistance, 78 ... Buffer, 80 ... Resistance, 82 ... Differential amplification , 100 ... signal generator, 110 ... determining unit, 200 ... test apparatus, 300 ... device under test

Claims (12)

A signal generator that generates a signal according to an input signal,
An integration circuit for integrating the input signal, including an integration capacitor and a series resistor provided in series;
A signal generator in which at least one of the capacitance of the integrating capacitor and the resistance value of the series resistor is variable. An adjustment unit that receives circuit information indicating a time constant of a band limiting circuit connected to a subsequent stage of the integration circuit, and adjusts at least one of the capacitance of the integration capacitor and the resistance value of the series resistor based on the circuit information. The signal generator according to claim 1. A band limiting circuit connected to a subsequent stage of the integrating circuit;
The signal generator according to claim 2, wherein the adjustment unit adjusts at least one of a capacitance of the integration capacitor and a resistance value of the series resistance based on a time constant of the band limiting circuit. The band limiting circuit has a limiting capacitor and a limiting resistor,
The adjustment unit is configured so that the product of the capacitance of the integration capacitor and the resistance value of the series resistor is equal to the product of the capacitance of the limiting capacitor and the resistance value of the limiting resistor. The signal generator according to claim 3, wherein at least one of the resistance values is adjusted. A signal generator that generates a signal according to an input signal,
An integration circuit to which the input signal is input;
A band limiting circuit connected to the subsequent stage of the integrating circuit,
The integration circuit is provided in series and includes an integration capacitor to which the input signal is input and a series resistance.
A signal generator having a time constant corresponding to a product of a capacitance of the integrating capacitor and a resistance value of the resistor equal to the time constant of the band limiting circuit. The signal generator according to claim 1, further comprising a current source that inputs a constant current signal to the integrating circuit. Compensation circuit that includes an RC series circuit having a time constant equal to a time constant of an equivalent circuit of dielectric absorption in the integration capacitor, and compensates for distortion caused by dielectric absorption of the integration capacitor that occurs in a signal output from the integration circuit The signal generator according to claim 1, further comprising: The signal according to claim 7, wherein the compensation circuit adds and subtracts a compensation signal obtained by limiting a band of a signal output from the integration circuit by the RC series circuit and a signal output from the integration circuit. Generator. The signal generator according to claim 8, wherein the compensation circuit adds and subtracts the signal output from the integration circuit and the compensation signal according to a ratio of a capacitance of the integration capacitor and an equivalent capacitance of the dielectric absorption. A test apparatus for testing a device under test,
A signal generator according to any one of claims 1 to 9, which generates a signal according to an input signal and inputs the signal to the device under test.
A test apparatus comprising: a determination unit that determines pass / fail of the device under test based on an operation of the device under test. A signal generation method for generating a signal according to an input signal,
A signal generation method for inputting the input signal to an integrating circuit including an integrating capacitor and a series resistor provided in series, wherein at least one of a capacitance of the integrating capacitor and a resistance value of the series resistor is variable. A test method for testing a device under test,
An integrating circuit including an integrating capacitor and a series resistor provided in series, wherein at least one of the capacitance of the integrating capacitor and the resistance value of the series resistor is variable, an input signal is input to generate a signal, and the device under test Type in the device,
A test method for determining pass / fail of the device under test based on the operation of the device under test.

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