| 摘要 |
PURPOSE:To enable accurate test and measurement, by controlling current values of first and second variable constant current circuits according to a slew rate value of a rear stage amplifier. CONSTITUTION:In a range below the maximum slew rate value of a rear stage buffer amplifier 9, an output level setting circuit 7 controls current values I1 and I2 of first and second variable constant current circuits 3 and 4 according to a difference value between first and second DC voltages VIH and VIL so that the rise time or fall time of an output side signal waveform becomes constant. When the difference value exceeds a value corresponding to a specified slew rate below the maximum slew rate value, the current values I1 and I2 are controlled to be constant so that the rise time or fall time of an output signal waveform becomes constant regardless of the amplitude of an output voltage. Regarding the maximum slew rate value, this can bring the slew rate value to a fixed value close to the maximum thereof thereby making a test and measurement more accurate as conducted varying the amplitude of an output waveform.
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