the local oscillator in a miniature fm receiver the output signal has a voltage equal to either an afc signal voltage for afc operation of the receiver or a reference voltage for synthesized operation of the receiver the afc switch circuitry employs bipolar transistors in current mirror configurations to minimize voltage offset and to enhance isolation between the unselected input and the output while operating on a power supply voltage less than 3 volts application_number US 37336989 A description fig1 is a block diagram of an fm receiver that incorporates an afc switch 72 in accordance with the present invention the organization and operation of the receiver shown in fig1 is disclosed in detail in commonly assigned ser no 213 719 referenced above briefly the receiver 8 includes an rf stage 10 an if stage 12 and a base band stage 14 a synchronous detector includes a mixer 49 injected with a 10 7 mhz signal in the embodiment of the circuit shown herein the synchronous detector provides a differential detector input signal along path 51 through amplifier 74 to afc switch 72 amplifier 74 converts the signal to a single ended signal the other input to afc switch 72 is a reference voltage additionally afc switch 72 has a select input the select input receives a binary select signal the voltage.