| 摘要 |
PURPOSE:To prevent the production of transient oscillation in the amplifier and that of interferring voltage to external circuits by clamping the output voltage of amplifier to a given voltage during the period immediately after and before the power down. CONSTITUTION:The reception signal Vin is input to the terminal 11 and fed to the amplifier 12, and no signal Vin is for a certain period. This no-input period is detected at the monitor circuit and the power down command signal PD is fed to the terminal 24. The control circuit 23 of the interface 21 receives the signal PD, the switch switching control signal PS is fed to the switch 22 for closing, and the output of the amplifier 12 is clamped to a given voltage (ground). Next, the circuit 23 delivers the power down command signal PD to the terminal 13 with somewhat delay. When the signal PD is released, the circuit 23 first releases the signal PD, and the switch 22 is OFF with a slight delay than it. Accordingly, the output of the amplifier 12 at the transient period of application of the signal PD and release is clamped at the ground voltage and the interference to the external circuit C is prevented. |
