| 摘要 |
An amplitude adjust circuit (10) provides a scaled representation (36) of an analog audio signal (28) with substantially zero DC offset relative to a reference voltage. A voltage reference generator (12) produces a voltage reference (20) that inputs to an operational amplifier (14). The offsetting circuit (16) offsets an analog audio signal (28) by a DC component substantially equal to the voltage reference (20) and provides the result as an input to the operational amplifier (14). The operational amplifier (14) produces an output with a DC component substantially equal to the voltage reference (20). The impedance network (18) operably couples to the operational amplifier (14) output and to the voltage reference (20) so that both sides of the impedance network (18) are held at the voltage reference (20) level. Based on a amplitude select signal (36), one of a plurality of impedances (32) of the impedance network (18) is selected to provide a scaled representation (36) of the analog audio signal (28) with substantially zero DC offset. <IMAGE>
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