Automatic gain control circuit

Details Automatic gain control circuit Automatic gain control circuit

1989-01-24

1989-11-28

Peng, John K.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358 27, 455239, 330281, H04N 552, H04N 964

Patent

active

048841412

ABSTRACT:
The gain of a video intermediate frequency signal processing circuit (11) is varied in accordance with the charge voltage of a capacitor (C.sub.1). The capacitor (C.sub.1) is charged with a relatively small current when the peak of a video detection signal does not reach a reference voltage (V.sub.A) and discharged with a relatively large current when reaches. A current source (29) for rapid charge is activated when the peak of the video detection signal does not reach the reference voltage (V.sub.A) over a predetermined period longer than one horizontal synchronous period, to rapidly charge the capacitor (C.sub.1). Thus, a speed in increase of the gain of the video intermediate frequency signal processing circuit is quickened, to hasten the restoration of an amplitude of the video detection signal.

REFERENCES:
patent: 3624290 (1971-11-01), Hofmann
patent: 3898380 (1975-08-01), Wilcox
patent: 4292598 (1981-09-01), Yasumura
patent: 4300104 (1981-11-01), Tanaka et al.
patent: 4371842 (1983-02-01), Lee
patent: 4433304 (1984-02-01), Engle
patent: 4807035 (1989-02-01), Sayliss

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