Single Chip FM Radio Circuit

his extremely simple FM radio receiver circuit is made possible by the special purpose TDA7000 IC. It integrates nearly all the functions necessary to build an FM receiver needing only a few external capacitors and a tuning circuit. Using a simple active RC filter made of only a single inductor, a few resistors and a varicap, this FM receiver will pick up broadcast radio between about 88 and 108 MHz. The mono output signal can then be used to drive a set of high impedance headphones, or feed a power amplifier.

Schematic

Parts

Part Total Qty. Description Substitutions C1, C9, C12, C17 4 0.1uF Ceramic Disc Capacitor C2, C4, C5, C6, C13 5 0.01uF Ceramic Disc Capacitor C3 1 20pF Ceramic Disc Capacitor See Notes C7, C15, C16 3 0.001uF Ceramic Disc Capacitor C8, C10, C11 3 220pF Ceramic Disc Capacitor C14 1 100pF Ceramic Disc Capacitor C18 1 200pF Ceramic Disc Capacitor R1 1 22K 1/4W 5% Resistor R2 1 100K 1/4W 5% Resistor R3 1 100K Linear Taper Pot D1 1 Motorola MV209 Varicap VHF Tuning Diode U1 1 TDA7000 FM Radio IC See Notes L1 1 7 Turn Inductor (See Notes) MISC 1 Board, Wire, Socket For U1, Case

Notes

1. Unfortunately, the TDA7000 went obsolete a few years ago. The original version is made by Signetics (now Philips) and is getting a bit hard to find these days. There are, however, other options. Philips makes the TDA7010T which is a surface mount version. The TDA7021T is also available which includes stereo capability. They are electrically similar but are only 16 pin chips so you'll need to compare the datasheets to build the circuit.
2. The value of C3 is noncritical and can be between 10pF and 20pF. Minor adjustments to L1 may be required based on the value of C3.
3. L1 is made by winding 7 turns of 24 AWG wire around pencil. Remove the pencil and then space the turns slightly.
4. Frequency selection is via R3.