| 摘要 |
PURPOSE:To prevent malfunctions of an amplfier and obtain a rapid output signal, by supplying a power source to a stabilizing circuit and by detecting rise of output voltages of the power source and the stabilizing circuit to cut off the AGC signal during detection of rise. CONSTITUTION:A muting circuit is constituted with the first and the second differential amplifiers A and B, bias circuit 10, and so on. The signal from input terminal 1 of the circuit constituted in this manner is amplified by transistors 2 and 3 of amplifier A to generate the output at terminal 6, and simultaneously, the output signal is supplied to the base of transistor 3 and is subjected to negative feedback. Further, the output signal is applied to the base of one transistor 16 of amplifier B through the time constant circuit consisting of transistor 13, capacitor 14, and resistance 15, and the voltage of capacitor 9 connected to the output circuit is supplied to the base of the other transistor 17, and variable impedance element 20 is controlled by the collector of transistor 16, thus subjecting the circuit to AGC. Thus, the AGC is cut off during a prescribed period for power supply. |
