AUTOMATIC FREQUENCY CHARACTERISTIC CONTROL CIRCUIT

PURPOSE:To obtain a stable and sharp picture at all times, by detecting an amplitude of control signal taking bit synchronism in character and figure information signals, controlling the frequency characteristics of a video amplifier circuit in response to the detected signal, and improving data error of the figure information. CONSTITUTION:A signal from a composite video signal input terminal 1 is amplified, a synchronizing signal is separated at a synchronizing separation circuit 4 and a signal to pick up character and figure information from a pickup signal generating circuit 5 is outputted with the synchronizing signal. The control signal from the circuit 5 is applied to a switch circuit 17 and a character information pickup signal generating circuit 23 and the circuit 17 applies the synchronizing control signal from a video frequency characteristic control circuit 14 to a detection circuit 18. The circuit 18 detects the level of a bit synchronism control signal to control a switch circuit 20. A peak detection circuit 21 detects the peak value for bit synchronism, the detected output controls the control circuit 14 to keep the frequency characteristic of a video signal from a video signal output terminal 30 constant at all times and to output an excellent video signal.