PURPOSE: To control independently two control terminals individually by using a DC bias current comprising a current from the 1st current source circuit and a current shared by a branching means so as to decide the gain of a signal amplification means.
CONSTITUTION: Differential transistor (TR) pair Q5, Q6 constitute the branching means. In setting the entire DC bias current IE of, e.g., a differential amplifier 2, the two control terminals VC1, VC2 adjust the 1st control circuit C1. When the set value is changed in a predetermined range, the voltage of the 2nd control circuit C2 is changed. The range of change is set to (n+1) times or it by selecting optionally the emitter area of a TR Q4 to n-time of that of a TR Q3. In using the circuit for a white balance circuit of a video camera, the terminal VC1 is used for a control terminal for accurate basic adjustment and the terminal VC2 is used for a control terminal of the white balance automatic control circuit.
YANO TAKASHI
SHIZUKUISHI MAKOTO
MURAYAMA TAKASHI
KONDO RYUJI
