PURPOSE: To make the gain of a first amplifier large, and to make the difference of a signal level for every field small by smoothing a detected signal into a DC component.
CONSTITUTION: The signal of an optional level inputted from an input terminal 1 is outputted through a gain variable circuit 2, and this signal is detected by a detecting circuit 4. The detected signal is turned into the DC component by a smoothion circuit 6, and is amplified by the first amplifier 5, and is transmitted to the sample hold circuit 7 of a following stage for each field. A control signal 9 held by each field is fed back for each field to the gain variable circuit 2, and the gain is controlled automatically for each field. After detecting the signal, smoothing the signal into the DC component by the smoothing circuit 6 before passing through the amplifier in such a way, the dynamic range of the first amplifier 5 can be expanded, and besides, the difference of the output level between the fields can be made smaller.
KINUGASA NORIHIDE
YOSHIMURA KOICHI
SAKA YOSHIMITSU
IOI TOSHIAKI
