This is the automatically search schematic diagram of FM radio. Its core component is a TDA7088 integrated circuit which includes FM radio receiver, antenna, oscillator, mixer, AFC ( frequency automatic control) circuit, intermediate frequency amplifier ( IF frequency is 70kHz), IF limiter, IF filter, frequency discriminator, low frequency squ
elch circuit and audio output; it also specifically sets search tuning circuit, signal detection circuit and frequency locked loop. It can use a varactor diode to replace the variable capacitor is, which is a special kind of diodes. The PN junction capacitance is changed with the bias voltage ( reverse voltage) on PN junction.