JP4714094B2 - Signal generator and test device - Google Patents

Description

  The present invention relates to a signal generator for generating a signal, a test apparatus for testing a device under test, and a PLL circuit. In particular, the present invention relates to a signal generator that generates a signal whose amplitude is controlled to be substantially constant.

  2. Description of the Related Art Conventionally, an ALC (Automatic Level Control) circuit is known as a circuit that controls and outputs a signal such as an RF signal substantially constant. The ALC circuit is a circuit that controls the amplitude of the output signal to be substantially constant by detecting the amplitude of the output signal and feeding back the detection result.

  FIG. 6 is a diagram showing a configuration of a conventional ALC circuit 400. The ALC circuit 400 includes a voltage variable attenuator 410, an amplifier 420, a coupling circuit 430, a detection circuit 440, and a comparator 450, and controls the amplitude of a high-frequency input signal.

  The voltage variable attenuator 410 attenuates the amplitude of the input signal with a predetermined attenuation factor and outputs the attenuated signal. The amplifier 420 outputs an output signal obtained by amplifying the output of the voltage variable attenuator 410 with a predetermined amplification factor. The detection circuit 440 detects the amplitude of the output signal received via the coupling circuit 430 and outputs a DC voltage of a level corresponding to the amplitude value of the output signal. When detecting the amplitude of the high frequency signal, a diode detection circuit is used as the detection circuit 440.

  The comparator 450 compares the level of the DC voltage output from the detection circuit 440 with a preset reference value, and controls the attenuation rate in the voltage variable attenuator 410 according to the comparison result. With such a configuration, an output signal having a substantially constant amplitude is generated. Since related patent documents and the like are not currently recognized, the description thereof is omitted.

  However, when a diode detection circuit is used as the detection circuit 440, the gain of the output voltage of the detection circuit 440 with respect to the amplitude of the output signal varies depending on the amplitude of the output signal. In general, the gain of the diode detection circuit varies exponentially with respect to the amplitude of the output signal. For this reason, the amplitude of the output signal cannot be accurately controlled.

  On the other hand, a configuration in which a log amplifier is provided between the detection circuit 440 and the comparator 450 is conceivable. Since the gain of the log amplifier changes with a logarithmic function with respect to the output level of the detection circuit 440, the characteristic of the exponential function in the detection circuit 440 can be canceled and the feedback loop band can be made substantially constant. However, the characteristics of the log amp change greatly with changes in temperature. For this reason, even when a log amplifier is used, it is difficult to accurately control the amplitude of the output signal. In addition, when the ALC circuit 400 is used in an electronic device test apparatus, it is difficult to accurately test the electronic device.

  Therefore, an object of the present invention is to provide a signal generator, a test apparatus, and a PLL circuit that solve the above-described problems. This object is achieved by a combination of features described in the independent claims. The dependent claims define further advantageous specific examples of the present invention.

In order to solve the above-described problem, according to a first aspect of the present invention, there is provided a signal generator for generating an output signal having a preset amplitude value, wherein the amplitude of the input signal is set to the voltage value of the given control signal. An amplitude control unit for controlling and outputting the output signal, a diode for detecting the output signal, an amplitude detection unit for detecting the amplitude of the output signal, an amplitude value detected by the amplitude detection unit, and a preset amplitude An amplitude comparison unit that supplies a control signal having a voltage value corresponding to a difference from the value to the amplitude control unit, a transistor provided between a connection point of the amplitude comparison unit and the amplitude control unit, and a ground potential, and an output signal Output signal detected by the amplitude detector, having a gain conversion circuit that controls the gate voltage applied to the transistor according to the level of the DC voltage according to the amplitude of the signal and controls the impedance between the connection point and the ground potential Amplitude of Based on, to provide a signal generator and a correcting unit for correcting the voltage value of the control signal.

The signal generator may further include an amplifying unit that amplifies the signal output from the amplitude control unit with a preset amplification factor and generates an output signal. The amplitude detection unit outputs a DC voltage with a gain that differs for each amplitude of the output signal of the amplification unit, and the correction unit sets the level of the DC voltage output by the amplitude detection unit in order to correct the gain difference in the amplitude detection unit. Based on this, the voltage value of the control signal may be corrected.

The amplitude detection unit is a correction coefficient whose value changes approximately exponentially according to the amplitude of the output signal, and the correction unit is a correction coefficient whose value changes approximately logarithmically according to the amplitude of the output signal. May be corrected.

The gain conversion circuit may output a gate voltage at a level obtained by correcting the DC voltage level with a coefficient based on the gain characteristic of the amplitude detection unit and the impedance characteristic of the transistor.

The signal generator includes a diode characteristic measurement unit that measures a gain characteristic with respect to an amplitude of an output signal in an amplitude detection unit, a transistor characteristic measurement unit that measures an impedance characteristic with respect to a gate voltage level in a transistor, and a gain characteristic. And a correction coefficient calculation unit that calculates a coefficient to be set in the gain conversion circuit based on the impedance characteristics and sets the coefficient in the gain conversion circuit.

The correction unit may further include a resistor provided between the transistor and the connection point, and a capacitor provided between the resistor and the connection point.

In the second embodiment of the present invention, a test apparatus for testing a device under test, a signal generator for inputting a test signal having an amplitude value set in advance in the device under test, and a signal output from the device under test A signal generator that controls and outputs the amplitude of the input signal in accordance with the voltage value of the given control signal, and a test. It has a diode that detects the signal and detects the amplitude of the test signal, and the amplitude of the control signal having a voltage value corresponding to the difference between the amplitude value detected by the amplitude detector and a preset amplitude value Amplitude comparison unit supplied to the control unit, a transistor provided between the connection point of the amplitude comparison unit and the amplitude control unit, and the ground potential, and a transistor according to the level of the DC voltage corresponding to the amplitude of the test signal Give gate A correction unit that has a gain conversion circuit that controls the pressure and controls the impedance between the connection point and the ground potential, and corrects the voltage value of the control signal based on the amplitude of the test signal output from the amplitude detection unit A test apparatus is provided.

The test apparatus may further include an amplification unit that amplifies the signal output from the amplitude control unit with a preset amplification factor and generates a test signal.

  The above summary of the invention does not enumerate all the necessary features of the present invention, and sub-combinations of these feature groups can also be the invention.

  Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the invention according to the scope of claims, and all combinations of features described in the embodiments are included. It is not necessarily essential for the solution of the invention.

  FIG. 1 is a diagram illustrating an example of a configuration of a signal generation device 100 according to an embodiment of the present invention. The signal generator 100 is a circuit that generates an output signal having a preset amplitude value, and includes an amplitude control unit 10, an amplification unit 20, an amplitude detection unit 30, an amplitude comparison unit 40, a DAC 50, and a correction unit 60. Prepare.

  The amplitude control unit 10 receives an input signal and controls the amplitude of the input signal. For example, the input signal is a high-frequency signal such as an RF signal. Further, the amplitude control unit 10 controls the amplitude of the input signal according to the voltage value of the given control signal. The amplitude controller 10 may be a variable voltage attenuator that attenuates the amplitude of the input signal at a predetermined attenuation rate. In this case, the amplitude control unit 10 may attenuate the input signal, for example, by controlling the impedance of the path for transmitting the input signal according to the voltage value of the control signal. The amplification unit 20 amplifies the signal output from the amplitude control unit 10 with a preset amplification factor, and generates an output signal.

  The amplitude detection unit 30 detects the amplitude of the output signal output from the amplification unit 20. The amplitude detection unit 30 in this example includes a coupling unit 32 and a detection unit 34. The coupling unit 32 is coupled to a transmission path that transmits an output signal between the output end of the amplification unit 20 and the output end of the signal generation device 100, and supplies a signal corresponding to the output signal to the detection unit 34. The coupling unit 32 may be coupled to the transmission path by, for example, inductive coupling.

  The detector 34 detects a signal given according to the output signal. That is, the detection unit 34 outputs a DC voltage having a level corresponding to the amplitude of a given signal. The detection unit 34 in this example is a diode detection circuit having a diode that rectifies a given signal and outputs a DC voltage having a level corresponding to the amplitude of the signal.

  The amplitude comparison unit 40 supplies a control signal having a voltage value corresponding to a difference between the amplitude value detected by the amplitude detection unit 30 and a preset amplitude value to the amplitude control unit 10. In this example, the level of the DC voltage output by the amplitude detector 30 is given as the amplitude value detected by the amplitude detector 30, and the level of the DC voltage output by the DAC 50 is given as a preset amplitude value. The DAC 50 is supplied with digital data that defines the amplitude that the output signal should have, and outputs a DC voltage corresponding to the digital data.

  The amplitude comparison unit 40 in this example includes a differential circuit 42, a resistor 44, and a capacitor 46. The differential circuit 42 receives the DC voltage output from the amplitude detector 30 and the DC voltage output from the DAC 50, and outputs a control voltage at a level corresponding to the difference between these DC voltages. The resistor 44 is provided between the output terminal of the differential circuit 42 and the control signal input terminal of the amplitude control unit 10, and the capacitor 46 is provided between the input terminal and the output terminal of the differential circuit 42. .

  The correction unit 60 corrects the voltage value of the control signal based on the amplitude of the output signal detected by the amplitude detection unit 30. The amplitude detection unit 30 outputs a DC voltage having a level corresponding to the amplitude of the output signal with a gain that differs for each amplitude of the output signal of the amplification unit 20. On the other hand, the correction unit 60 corrects the voltage value of the control signal based on the level of the DC voltage output from the amplitude detection unit 30 in order to correct the gain difference in the amplitude detection unit 30.

  In this example, since the detection unit 34 is a diode detection circuit, the gain of the detection unit 34 changes substantially in an exponential function according to the amplitude of the output signal. On the other hand, the correction unit 60 corrects the voltage value of the control signal with a correction coefficient whose value changes approximately in a logarithmic function according to the amplitude of the output signal. The correction unit 60 in this example includes a capacitor 62, a resistor 64, a transistor 66, and a gain conversion circuit 68. Here, the amplitude of the output signal may be the amplitude of the signal input from the coupling unit 32 to the detection unit 34, or may be the amplitude of the signal output from the amplification unit 20.

  The capacitor 62 is provided between the connection point between the output terminal of the amplitude comparison unit 40 and the control signal input terminal of the amplitude control unit 10 and the ground potential. The resistor 64 is provided in series between the capacitor 62 and the ground potential, and the transistor 66 is provided in series between the resistor 64 and the ground potential. For example, the resistor 44, the capacitor 62, the resistor 64, and the transistor 66 may constitute a lag lead filter.

  The gain conversion circuit 68 controls the gate voltage applied to the transistor 66 according to the level of the DC voltage output from the amplitude detector 30, and controls the impedance between the connection point and the ground potential. For example, the gain conversion circuit 68 is an operational amplifier, which amplifies the level of the DC voltage output from the amplitude detector 30 with a predetermined amplification factor and inputs it to the gate terminal of the transistor 66. The value of the impedance of the transistor 66 changes approximately in a logarithmic function according to a given gate voltage. Therefore, the gain characteristic in the amplitude detector 30 can be canceled out, and the feedback loop gain can be made substantially constant regardless of the level of the output signal. By making the loop gain substantially constant, the feedback loop band can be made substantially constant regardless of the level of the output signal.

  FIG. 2 is a diagram illustrating an example of the gain characteristic of the amplitude detector 30, the impedance characteristic of the transistor 66, and the loop band characteristic of feedback with respect to the level of the output signal. 2A shows an example of the gain characteristic of the amplitude detector 30, FIG. 2B shows an example of the impedance characteristic of the transistor 66, and FIG. 2C shows an example of the loop band characteristic. .

  As described above, since the amplitude detection unit 30 detects the output signal using a diode, the gain characteristic of the amplitude detection unit 30 is substantially an exponential function according to the voltage of the output signal as shown in FIG. Change.

  On the other hand, when the transistor 66 is regarded as an equivalent resistance, the impedance changes approximately in a logarithmic function according to a given gate voltage. The transistor 66 may be a JFET, for example. Since the gate voltage output from the gain conversion circuit 68 changes according to the level of the output signal, the impedance of the transistor 66 changes approximately in a logarithmic function according to the level of the output signal, as shown in FIG. To do.

  Since the control voltage is attenuated according to the impedance of the transistor 66, the zero point of the lag lead filter changes. For this reason, the feedback loop gain is substantially constant regardless of the level of the output signal, and the feedback loop band is substantially constant as shown in FIG.

  However, the gain characteristic of the amplitude detection unit 30 is not necessarily completely canceled out by the gain characteristic of the amplitude detection unit 30 and the impedance characteristic of the transistor 66. The gain conversion circuit 68 may adjust the level of the gate voltage so that the loop gain with respect to the level of the output signal within a predetermined range is the most uniform. For example, the gain conversion circuit 68 may adjust the gate voltage level by performing a predetermined calculation on the level of the input DC voltage. The gain conversion circuit 68 may perform the calculation using the same coefficient for each level of the input DC voltage, or may perform the calculation using a different coefficient. The gain conversion circuit 68 may amplify and adjust the level of the input DC voltage with a predetermined amplification factor, and may add or subtract a predetermined offset value to or from the DC voltage level. The gain conversion circuit 68 may change the amplification factor and / or the offset value for each DC voltage level.

  The signal generator 100 may further include means for calculating a coefficient to be used for the calculation in the gain conversion circuit 68 based on the gain characteristic of the amplitude detector 30 and the impedance characteristic of the transistor 66 and setting the coefficient in the gain conversion circuit 68. .

  FIG. 3 is a diagram illustrating another example of the configuration of the signal generation device 100. The signal generating apparatus 100 in this example further includes a diode characteristic measuring unit 70, a transistor characteristic measuring unit 80, and a correction coefficient calculating unit 90 in addition to the configuration of the signal generating apparatus 100 described with reference to FIG. Other constituent elements may be the same as those given the same reference numerals in FIG.

  The diode characteristic measurement unit 70 measures the gain characteristic with respect to the amplitude of the output signal in the amplitude detection unit 30. For example, the diode characteristic measurement unit 70 inputs the measurement signals whose amplitudes are sequentially changed to the amplitude detection unit 30, and measures the level of the DC voltage output from the amplitude detection unit 30 for each measurement signal. The gain characteristic may be measured.

  The transistor characteristic measurement unit 80 measures the characteristic of impedance with respect to the level of the gate voltage in the transistor 66. For example, the transistor characteristic measuring unit 80 may measure the impedance characteristic by inputting the gate voltage whose level is sequentially changed to the transistor 66 and measuring the impedance of the transistor 66 with respect to each gate voltage. For example, the transistor characteristic measurement unit 80 may measure the value of the current flowing through the transistor 66 by detecting the voltage across the resistor 64 and calculate the impedance of the transistor 66 by measuring the voltage between the source and emitter of the transistor 66. .

  Based on the gain characteristic of the amplitude detector 30 and the impedance characteristic of the transistor 66, the correction coefficient calculator 90 calculates a coefficient to be set in the gain conversion circuit 68 so that the loop gain of the feedback becomes substantially constant. .

  In addition, the transistor characteristic measurement unit 80 measures the impedance characteristic of the transistor 66 by inputting the measurement signal whose amplitude is sequentially changed to the amplitude detection unit 30 and measuring the impedance of the transistor 66 with respect to each measurement signal. May be. In this case, since both the gain characteristic of the amplitude detector 30 and the impedance characteristic of the transistor 66 can be measured with respect to the amplitude of the measurement signal, the coefficient to be set in the gain conversion circuit 68 can be easily obtained.

  Further, the correction coefficient calculation unit 90 inputs measurement signals whose amplitudes are sequentially changed to the amplitude detection unit 30, measures the control signals input to the amplitude control unit 10 for the respective measurement signals, and measures the measurement signals. The coefficient to be set in the gain conversion circuit 68 may be calculated so that the gain of the control signal with respect to the amplitude of the gain becomes substantially uniform.

  The correction coefficient calculation unit 90 may calculate the same coefficient for each amplitude of the measurement signal. In this case, the correction coefficient calculation unit 90 may calculate a coefficient to be set in the gain conversion circuit 68 so that the variance of the gain of the control signal for each amplitude of the measurement signal is minimized. Further, the correction coefficient calculation unit 90 may calculate the coefficient for each amplitude of the measurement signal. In this case, the correction coefficient calculation unit 90 may calculate a coefficient for each amplitude of the measurement signal so that the gain of the control signal for each amplitude of the measurement signal is substantially the same.

  FIG. 4 is a diagram illustrating an example of the configuration of the test apparatus 200 according to the embodiment of the present invention. The test apparatus 200 is an apparatus for testing a device under test 500 such as a semiconductor circuit, and includes a pattern generator 210, a waveform shaper 220, a signal generator 100, a timing generator 230, a comparator 240, and a determiner 250. Prepare.

  The pattern generator 210 generates a test pattern for testing the device under test 500. For example, the pattern generator 210 generates a test pattern including a logical pattern of a test signal to be input to the device under test 500.

  The waveform shaper 220 generates a test signal to be input to the device under test 500 based on the test pattern. For example, the waveform shaper 220 generates a test signal indicating a voltage value corresponding to the logical pattern according to the period of the given timing signal.

  The timing generator 230 generates a timing signal. For example, the timing generator 230 generates a timing signal that defines the data rate of the test signal and supplies the timing signal to the waveform shaper 220.

  The signal generator 100 receives the test signal output from the waveform shaper 220, adjusts the amplitude of the test signal to a preset amplitude value, and inputs the test signal to the device under test 500. The signal generator 100 has the same function and configuration as the signal generator 100 described with reference to FIGS.

  The comparator 240 receives an output signal that the device under test 500 outputs in response to the test signal. The comparator 240 outputs a logic pattern of the output signal obtained by comparing the level of the output signal with a preset threshold value.

  The determiner 250 determines the pass / fail of the device under test 500 by comparing the logic pattern output from the comparator 240 with a predetermined expected value pattern. For example, the pattern generator 210 may generate the expected value pattern.

  With this configuration, the device under test 500 can be tested. Further, since the signal generator 100 can control the amplitude of the test signal with high accuracy, the device under test 500 can be tested with high accuracy.

  FIG. 5 is a diagram showing an example of the configuration of the PLL circuit 300 according to the embodiment of the present invention. The PLL circuit 300 is a circuit that generates an oscillation signal synchronized with a given reference signal, and includes a phase comparator 310, a loop filter 320, a DAC 360, an adder 340, a voltage control oscillator 350, and a frequency divider 370.

  The voltage controlled oscillator 350 generates an oscillation signal having a frequency according to a given control voltage. The frequency divider 370 generates a frequency-divided signal obtained by dividing the oscillation signal by a predetermined frequency dividing ratio, and inputs the frequency-divided signal to the phase comparator 310.

  The phase comparator 310 detects a phase difference between the reference signal and the divided signal and outputs a control voltage corresponding to the phase difference. The loop filter 320 passes a predetermined frequency component of the control voltage output from the phase comparator 310 and supplies it to the voltage controlled oscillator 350. With such a configuration, an oscillation signal synchronized with the reference signal can be generated.

  The DAC 360 receives digital data corresponding to the oscillation frequency of the oscillation signal, converts the digital data into an analog voltage, and outputs the analog voltage. The adder 340 superimposes the analog voltage on the control voltage input to the voltage controlled oscillator 350. With such a configuration, the DAC 360 and the addition unit 340 function as a frequency adjustment unit that preliminarily adjusts (pretunes) the frequency of the oscillation signal.

  However, the change in frequency with respect to the change in control voltage in the voltage controlled oscillator 350 does not necessarily change linearly. In particular, since the analog voltage output from the DAC 360 is an offset voltage of the control voltage, the gain of fluctuation in the frequency of the voltage controlled oscillator 350 with respect to the level of the control voltage output from the phase comparator 310 depends on the level of the analog voltage. May fluctuate significantly.

  For this reason, the loop filter 320 in this example corrects the voltage value of the control voltage passing through the loop filter 320 based on the level of the analog voltage output from the DAC 360, and compensates for the fluctuation in the gain of the voltage controlled oscillator 350. The loop filter 320 includes resistors 322, 326, 330, an operational amplifier 328, a capacitor 324, and a correction unit 60.

  The resistor 322 is connected between the output terminal of the phase comparator 310 and the negative input terminal of the operational amplifier 328. The capacitor 324 and the resistor 326 are provided in series between the negative input terminal and the output terminal of the operational amplifier 328. The resistor 330 is provided between the output terminal of the operational amplifier 328 and the adder 340. With such a configuration, the control voltage output from the phase comparator 310 is integrated.

  The correction unit 60 may function as a filter that removes a predetermined frequency component of the signal output from the operational amplifier 328. The correction unit 60 in this example includes a capacitor 62, a resistor 64, a transistor 66, and a gain conversion circuit 68. The capacitor 62 is provided between the output terminal of the operational amplifier 328 and the ground potential. The resistor 64 is provided between the capacitor 62 and the ground potential, and the transistor 66 is provided between the resistor 64 and the ground potential. With such a configuration, the capacitor 62, the resistor 330, the resistor 64, and the transistor 66 function as a lag lead filter.

  The gain conversion circuit 68 supplies a gate voltage corresponding to the analog voltage output from the DAC 360 to the transistor 66. With such a configuration, the gain difference in the voltage controlled oscillator 350 due to the analog voltage output from the DAC 360 can be compensated, and the loop band of the PLL circuit 300 can be made constant.

  The gain conversion circuit 68 described with reference to FIGS. 1 to 3 generates a gate voltage using a coefficient based on the characteristics of the amplitude detection unit 30 and the characteristics of the transistor 66. However, the gain conversion circuit 68 in this example uses voltage control. The gate voltage may be generated using a coefficient based on the characteristics of the oscillator 350 and the characteristics of the transistor 66. In this example, the coefficient to be set in the gain conversion circuit 68 may be calculated by the same configuration and method as those described in FIGS.

  According to the PLL circuit 300 in this example, gain variation in the voltage controlled oscillator 350 can be reduced, and a highly accurate oscillation signal can be generated.

  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.

  As can be seen from the above, according to the present invention, a signal whose amplitude is controlled with high accuracy can be generated. In addition, a highly accurate oscillation signal can be generated. In addition, the device under test can be tested with high accuracy.

It is a figure which shows an example of a structure of the signal generator 100 which concerns on embodiment of this invention. It is a figure which shows an example of the gain characteristic of the amplitude detection part 30, the impedance characteristic of the transistor 66, and the loop band characteristic of feedback with respect to the level of an output signal. 2A shows an example of the gain characteristic of the amplitude detector 30, FIG. 2B shows an example of the impedance characteristic of the transistor 66, and FIG. 2C shows an example of the loop band characteristic. . 6 is a diagram illustrating another example of the configuration of the signal generation device 100. FIG. It is a figure which shows an example of a structure of the test apparatus 200 which concerns on embodiment of this invention. It is a figure which shows an example of a structure of the PLL circuit 300 which concerns on embodiment of this invention. It is a figure which shows the structure of the conventional ALC circuit 400. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Amplitude control part, 20 ... Amplification part, 30 ... Amplitude detection part, 32 ... Coupling part, 34 ... Detection part, 40 ... Amplitude comparison part, 42 ... Difference Moving circuit, 44... Resistor, 46 .. capacitor, 60... Correction unit, 62 .. capacitor, 64 .. resistor, 66 .. transistor, 68. .. Diode characteristic measuring unit, 80... Transistor characteristic measuring unit, 90... Correction coefficient calculating unit, 100... Signal generator, 200. ..Waveformer, 230 ... Timing generator, 240 ... Comparator, 250 ... Determiner, 300 ... Device under test, 300 ... PLL circuit, 310 ... Phase comparator 320 ... Loop filter, 322 ... Resistance 324: capacitor, 326 ... resistor, 328 ... operational amplifier, 330 ... resistor, 340 ... adder, 350 ... voltage controlled oscillator, 360 ... DAC, 370 ... minute Circulator 400 ... Conventional ALC circuit 410 ... Voltage variable attenuator 420 ... Amplifier 430 ... Coupling circuit 440 ... Detection circuit 450 ... Comparator 500 ..Devices under test

Claims (9)

A signal generator for generating an output signal having a preset amplitude value,
An amplitude controller that controls and outputs the amplitude of the input signal according to the voltage value of the given control signal;
An amplitude detection unit having a diode for detecting the output signal and detecting the amplitude of the output signal;
An amplitude comparison unit that supplies the control signal having a voltage value corresponding to a difference between the amplitude value detected by the amplitude detection unit and the preset amplitude value to the amplitude control unit;
A transistor provided between a connection point of the amplitude comparison unit and the amplitude control unit and a ground potential, and a gate voltage applied to the transistor according to a level of a DC voltage corresponding to the amplitude of the output signal is controlled. A gain converting circuit that controls an impedance between the connection point and the ground potential, and correcting the voltage value of the control signal based on the amplitude of the output signal detected by the amplitude detector And a signal generator. The signal generator according to claim 1, further comprising an amplifying unit that amplifies a signal output from the amplitude control unit at a preset amplification factor and generates the output signal. The amplitude detection unit outputs the DC voltage with a gain different for each amplitude of the output signal of the amplification unit,
The signal generator according to claim 2 , wherein the correction unit corrects a voltage value of the control signal based on a level of the DC voltage output from the amplitude detection unit in order to correct a gain difference in the amplitude detection unit. . In the amplitude detection unit, the gain changes approximately in an exponential function according to the amplitude of the output signal,
Wherein the correction unit, the correction coefficient value at approximately logarithmic function according to the amplitude of the output signal changes, the signal generating apparatus according to any one of claims 1 to 3, correcting the voltage value of the control signal . 5. The gain conversion circuit according to claim 1, wherein the gain conversion circuit outputs the gate voltage at a level obtained by correcting the DC voltage level with a coefficient based on a gain characteristic of the amplitude detection unit and an impedance characteristic of the transistor . The signal generator according to one item . In the amplitude detection unit, a diode characteristic measurement unit that measures a characteristic of the gain with respect to the amplitude of the output signal;
A transistor characteristic measuring unit for measuring a characteristic of the impedance with respect to a level of the gate voltage in the transistor;
6. The correction coefficient calculation unit according to claim 5, further comprising: a correction coefficient calculation unit configured to calculate the coefficient to be set in the gain conversion circuit based on the gain characteristic and the impedance characteristic, and to set the coefficient in the gain conversion circuit. Signal generator. The correction unit is
A resistor provided between the transistor and the connection point;
The signal generator according to claim 4, further comprising a capacitor provided between the resistor and the connection point. A test apparatus for testing a device under test,
A signal generator for inputting a test signal having a preset amplitude value to the device under test;
A determination unit that determines whether the device under test is good or bad based on a signal output from the device under test;
The signal generator is
An amplitude controller that controls and outputs the amplitude of the input signal according to the voltage value of the given control signal;
An amplitude detection unit having a diode for detecting the test signal and detecting the amplitude of the test signal;
An amplitude comparison unit that supplies the control signal having a voltage value corresponding to a difference between the amplitude value detected by the amplitude detection unit and the preset amplitude value to the amplitude control unit;
A transistor provided between a connection point of the amplitude comparison unit and the amplitude control unit and a ground potential, and a gate voltage applied to the transistor according to a level of a DC voltage corresponding to the amplitude of the test signal is controlled. A gain conversion circuit that controls an impedance between the connection point and the ground potential, and a correction for correcting the voltage value of the control signal based on the amplitude of the test signal output by the amplitude detection unit And a test apparatus. The test apparatus according to claim 8, further comprising an amplifying unit that amplifies a signal output from the amplitude control unit at a preset amplification factor and generates the test signal.

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