Patent ID: 6014180
Filing Date: 2000-01-11
Classification: H04N,Y10S

Abstract:
An automatic gain control loop circuit comprising:a variable-gain amplifier circuit, capable of controlling gain, for amplifying video signals that are alternately input thereto from two channels, and for outputting an output signal;a level detector circuit for detecting a level of a signal derived from the output signal of the variable-gain amplifier circuit and for outputting a first signal and a second signal having a level substantially proportionate to a level of the first signal;a first capacitor for low-pass filtering and storing the first signal output from the level detector circuit;a second capacitor for low-pass filtering and storing the second signal output from the level detector circuit during a signal period of a second channel included in the two channels;an adder circuit for adding the second signal stored by the second capacitor to the first signal stored by the first capacitor; anda switch circuit for selecting the first signal stored in the first capacitor during a signal period of a first channel included in the two channels and selecting an output from the adder circuit during the signal period of the second channel, and for feeding a selected signal back to a gain control input terminal of the variable-gain amplifier circuit.