| 摘要 |
A bias control circuit and an associated method in an audio output amplifier provide slow turn-on or turn-off operation of a bias voltage generation circuit, using an external bypass capacitor. A slow rate in the turn-on and turn-off operations in such a bias voltage generation circuit prevents click or pop noises. In one embodiment, two bipolar transistors each responsive to the voltage on an external capacitor are provided to gradually increase the voltage of an output node, which can be used to drive the gate terminal of an MOS transistor in the bias voltage generation circuit. Alternatively, in another embodiment, an MOS inverter, which receives as input the voltage on bypass capacitor, is provided to divert current from a conventional bias circuit. The rate at which the MOS inverter diverts current from the conventional bias circuit controls the slew rate in the turn-off operation of the bias current. Adjustment to this slew rate can be accomplished by adjusting the resistance and capacitance values of resistor and bypass capacitor, respectively.
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