This FM transmitter circuit is small, similar to our previous single chip FM  transmitter, but this FM transmitter is monophonic. You can see in the circuit’s schematic, the left and right signals is mixed before modulate the radio frequency. Here is the schematic diagram of the circuit:

single chip small fm transmitter circuit schematic

 

The core of this FM transmitter circuit is a MAX2606  IC chip, a compact, high-performance intermediate-frequency (IF) voltage-controlled oscillators (VCOs).  This FM transmitter will output -21 dBm radiation power, and work with 3 volts power supply. Two small 1.5V battery cells  should be enough to power this FM transmitter circuit. The best part of this FM transmitter circuit is that you just need a potentiometer to tune the frequency within commercial FM broadcst band 88-108 MHz. This chip provide all the necessery frequency tuning circuitry, you don’t even need an external varactor. You can use this FM transmitter circuit to extend your mp3/CD player in your room to your portable set around the house, a simpler way than using wires. [Circuit’s schematic diagram source: Maxim Integrated Products Application Notes]