| 摘要 |
PURPOSE:To keep the amplitude of a signal at a regulated level and to attain the compensation of a frequency characteristic by providing a negative feedback amplifier consisting of an AGC circuit and a feedback circuit having a prescribed frequency characteristic, and an AGC detection circuit which detects the amplitude of the output signal of the AGC circuit and controls the gain of the AGC circuit. CONSTITUTION:Since a negative feedback circuit 9 has the frequency characteristic, its frequency characteristic changes when the gain of an AGC circuit 7 changes. At such a case, the frequency characteristic of the circuit 9 is set so that the more negative feedback is applied at a low frequency range than a high frequency range. Therefore, even when a magnetic head 2 performs a reproducing scanning on a recording track 3 at an inner circumference side on a magnetic sheet 1 and a high-pass side is damped and an FM video signal of small amplitude can be obtained, a negative feedback quantity at the low-pass area is increased with the increase of the gain at the AGC circuit 7, the high- pass area being intensified. Thereby, the FM video signal in which the amplitude is set at the regulated level and the frequency characteristic is compensated can be obtained.
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