| 摘要 |
PURPOSE:To suppress rise at ambient temperature by using the 1st switch to disconnect DC coupling between a pre-stage amplifier circuit and a power amplifier circuit with no input signal, using the 2nd switch to disconnect the feedback circuit and providing a switch circuit applying feedback to the pre-stage amplifier circuit. CONSTITUTION:The switch circuit 4 consists of a relay 4-3 and contacts 4-1, 4-2 and the pre-stage amplifier circuit and the power amplifier circuit are connected directly. When a signal is inputted to a terminal IN, the relay 4-3 is activated, the pre-stage amplifier circuit 1 and the power amplifier circuit 2 are connected in cascade and a feedback circuit 5 is provided from the output of the power amplifier circuit 2 to the input of the pre-stage amplifier circuit and the amplified signal is sent externally. In this case, the power amplifier circuit 2 is heated and the connection between the prestage amplifier circuit 1 and the power amplifier circuit 2 is disconnected and the feedback is applied only to the pre-stage amplifier circuit 1 and a bias voltage fed via the pre-stage amplifier circuit 1 is lost, then the power amplifier circuit 2 is cut off and no current fllows. Thus, the mean heat dissipation is less than a conventional dissipation and the ambient temperature rise is lowered than a conventional rise.
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