| 摘要 |
PURPOSE:To change a high frequency cut-off frequency in transmission characteristics to a main signal of this circuit system, by negative-feeding back only the high frequency component and changing the closed gain with the gain change of the variable gain amplifying circuit. CONSTITUTION:A main signal to be amplified is applied to an input terminal 2, and the output is fed back to a feedback circuit 5. Since the feedback circuit 5 consists of a polarity inversion amplifier 51 and a high-pass circuit 52, the feedback is a negative feedback, and the amount of feedback is less at a low frequency and much in high frequency. Thus, the frequency characteristics from the input terminal 2 to an output terminal 3 are of high frequency decrease type, and when the gain of a variable gain amplifier 1 is increased, the closed loop gain of the feedback loop is increased, the high frequency drooping characteristics are emphasized, and when the gain of the amplifier 1 is decreased, the high frequency drooping characteristics are weakened. |
