| 摘要 |
PURPOSE:To prevent the oscillation due to the fact that the video intermediate frequency amplifying circuit has more gain than required, by controlling the output of the automatic gain control voltage generating circuit. CONSTITUTION:The voltage control circuit 6 is provided between the output terminal of the automatic gain control valtage generating circuit (AGC voltage generating circuit) 4 and the control voltage input terminal of the video intermediate frequency amplifying circuit (VIF circuit) 1. This control circuit 6 is provided with the emitter follower circuit consisting of a transistor Q8 and a resistor R3, and the constant-voltage circuit consisting of a constant-voltage element D6, a diode D5 and a resistor R4. Accordingly, the output voltage F is controlled by the voltage VD decided by the diodes D5, D6. In this way, when the output of the AGC voltage generating circuit 4 is controlled, it is possible to prevent the oscillation due to the fact that the VIF circuit has more gain than required. |
