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Patent Searching and Data


Title:
AUTOMATIC GAIN CONTROL CIRCUIT FOR VIDEO SIGNAL
Document Type and Number:
Japanese Patent JPS5862912
Kind Code:
A
Abstract:

PURPOSE: To attain the compatibility of the control characteristics at steady state and the transient response characteristics, by controlling a detection current circuit, a storage circuit and a switch circuit with two control signals and increasing the discharge time constant of a peak value detection circuit.

CONSTITUTION: When a video signal (a) is inputted at first, a large signal (b) is outputted from a gain variable amplifier 2. A peak value detection circuit 6 takes its peak value and a detection current (d) flows from a detection current detecting circuit 17, an output (f) of a storage circuit 20 holds the detection voltage and goes to low level. Next, when a control signal (e) is inputted, since the product between the signals (e) and (f) is a low level, a switch 21 is turned off. When a control signal (g) is inputted next, the signal (f) goes to a high level. Further, when the signal (e) is inputted, the product with the signal (f) goes to a high potential to turn on the circuit 21. Thus, a circuit 22 is connected to the circuit 6 and the detection voltage is lowered. Since the circuit 6 performs detection at each period of the signal (e), excellent transient response can be obtained even with a large time constant of the circuit 6. Further, the response at steady state is also excellent.


Inventors:
KONDOU KAZUO
Application Number:
JP16026981A
Publication Date:
April 14, 1983
Filing Date:
October 09, 1981
Export Citation:
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Assignee:
HITACHI LTD
International Classes:
H04N5/93; H03G3/20; H03G3/30; H04N5/53; (IPC1-7): H04N5/52; H04N5/93
Attorney, Agent or Firm:
Michito Hiraki