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Creating a HI-FI stereo FM transmitter to transmit music around the house or even for your own radio station can be sometimes really challenging. Designing preamplifiers, buffers, RF oscillators, modulators, and RF amplifiers add to the difficulty of building an FM transmitter. With this circuit, we can minimize the complexity of creating stereo FM transmitters.

This circuit uses a HI-FI Stereo FM Transmitter IC. This IC serves as the low power stage of the transmitter and it can be powered by a 1.25V-2.5V DC supply voltage. It consists of a stereo modulator that creates stereo composite signals, an FM modulator that creates FM signals, and an RF amplifier. The stereo modulator develops composite signals made up of a MAIN (L+R) signal, a SUB (L-R) signal, and a pilot (19kHz) signal using 38kHz crystal oscillator. The FM modulator has carriers on the broadcast band (88-108 MHz). The RF amplifier transmits the stereo encoded FM signals and is also a buffer for the FM modulator.

The MRFE6VP100HSR5 in this circuit serves as its RF Power LDMOS transistors. With the use of some components, the MRFE6VP100HSR5 acts as its power amplifier and amplifies the signal it receives from the stereo FM transmitter IC output. The MRFE6VP100HSR5 circuit is configured as a broadband power amplifier covering frequencies from 30MHz up to 512MHz. It can be supplied by a 50V power supply able to provide at least 100W power. The MRFE6VP100HSR5 can also provide 100W PEP power with a gain of 19.0dB.