| 摘要 |
PURPOSE:To make excellent the high frequency characteristics by increasing the freedom of circuit design, through giving the amplitude limit function to the differential amplifying circuit of the final stage of the video IF amplifying circuit and making adjustable the input amplitude value to the synchronizing detection circuit. CONSTITUTION:A pair of differential transistors Tr12, Tr13 are given to the third amplifying circuit 11 of the video IF amplifying circuit 2, the differential output of the second amplifier 10 is fed to the base, the load resistors 14, 15 are connected to the collector, and the emitter of the both Tr12, 13 is grounded through the constant current source 16. Further, the output of the circuit 2 is fed to the synchronizing detection circuit 4 from the collector of Tr13 of the circuit 2, and the output of the gain control circuit 5 controls the gain of the amplifying circuits 9 and 10. Thus, the amplitude limit function is given to the circuit 11 constituting the differential amplifying circuit of the final stage and the input amplitude value to the circuit 4 is made adjustable, allowing to increase the freedom of circuit design and to make excellent the high frequency characteristics. |
