Amplitude adjusting equipment in a signal translation line

摘要

An amplitude-adjusting circuit used for a contrast-adjusting circuit of resistor division type in which a video signal is applied across a pair of series-connected resistors and an output is produced from the junction point of the two resistors. At least one of the resistors is used as a variable resistor. The amplitude-adjusting circuit comprises a current source for supplying a constant current steadily between the terminals of the variable resistor, a high-gain amplifier for controlling the resistance value of the variable resistor, and a filter for separating the video signal component from the change of the value of the variable resistor represented by a voltage change, and introducing the resistance change to the high-gain differential amplifier.