| 摘要 |
PURPOSE:To decrease the effect of noise by allowing an averaging circuit to always test whether or not the gain set at present is enough so as to fix the gain when the control time intervals of the test is large. CONSTITUTION:A signal E representing the presence of an input digital signal and an U/-D signal representing to up/down gain are inputted to the averaging circuit 15 of an automatic gain control circuit and the circuit 15 applies +1 count or -1 count when the U or the inverse of D signal is significant and the clock T is led. The result of logic operation of an output from the circuit 15 is inputted to an U/D counter circuit 6 and a control time interval measuring counter circuit 7. When the circuit 6 counts many number of times from the minimum control interval and the count approaches the object level, the state is maintained. When the circuit 7 counts lots of number of times from the minimum revision interval and the gain approaches the object level, the gain is fixed by a JK-FF 8 to reduce the effect of noise.
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