| 摘要 |
2064804 9100654 PCTABS00003 An AFC switch circuit is controlled by a select input logic signal (switch) for providing a selected output signal to control the local oscillator in a miniature FM receiver. The output signal (from Q34) has a voltage equal to either an AFC signal voltage (IN+) for AFC operation of the receiver, or a reference voltage (VREF) for synthesized operation of the receiver. The AFC switch circuitry employs bipolar transistors in current mirror configurations (82, 84, 86) to minimize voltage offset and to enhance isolation between the unselected input and the output while operating on a power supply voltage (BANDGAP) less than 3 volts.
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