| 摘要 |
PURPOSE:To obtain a logarithmic amplifier operated stably even to an input pulse signal with a high duty ratio by adding a voltage clamping diode in parallel with a resistor for signal grounding of a video amplifier. CONSTITUTION:The voltage clamping diodes 25-30 are added in parallel with resistors 7-12 for signal grounding. In inputting a negative pulse signal to the input, when the duty ratio of the input signal is high, a reverse voltage to a signal proportional to the duty ratio is going to be generated at the input of the video amplifiers 13-17, the voltage is clamped to the ground level by the added diodes 25-30 and no reverse voltage is generated. Thus, the operating point of the input of the video amplifiers 13-17 is always 0V and no negative voltage is generated at an output of an operational amplifier 18 and a signal is outputted without increasing the amplitude. Even if the pulse width of the input signal is large and the sag is increased, the generation of the reverse voltage to the signal is prevented and distortion of waveform is prevented. |
