The recent availability of a broad line of truly high-performance consumer integrated circuits makes it possible to construct a high quality, low noise, low distortion and low cost AM/FM/Stereo receiver. This is the complete design circuit for AM/FM/Stereo Receiver. This is the figure of the circuit;
This circuit is using LM3089FM for control the operation in this circuit. The LM3089 FM IF System does all the major functions necessary for FM processing, including a three stage amplifier/limiter and balanced product detector, as well as an audio preamplifier. A single quadrature coil was used for ease of alignment; yielding recovered audio with THD less than 0.5%, however a double coil may be used to diminish THD to 0.1% if required. Carrier level detectors provide delayed AGC, SIGNAL strength meter drive, and adjustable inter station mute control R11. The internal AFC amplifier was used to drive the TUNING meter, giving a visual indication of center tuning. FM stereo demodulation is accomplished by the use of the LM1800 phase locked loop, thereby eliminating the need for external coils. Only two adjustments are necessary: R14, which sets the 19 kHz oscillator, and R17, which corrects which corrects for excess phase shift thru the IF stages, and yields maximum channel separation. Automatic stereo/ monaural switching is built-in, and may be used in lieu of mechanical switching if desired. The open collector lamp driver is used to light a LED whenever a stereo station is encountered.
[Schematic diagram source: National Semiconductor Notes]
[Schematic diagram source: National Semiconductor Notes]
