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TDA7000 is a great chip because it includes RF input stage, mixer, local oscillator, IF (intermediate frequency) Limiter, IF filter, amplifier, Phase demodulator, Mute detector, Frequency-Locked-Loop system and voltage controlled oscillator (VCO) all in a single chip, so you don’t have to do so much tuning and tweaking as you would normally do in super heterodyne receivers. TDA7000 is also a great choice for folks that don’t have great experience with RF circuits due to the fact that there are few external capacitors & resistors needed, no external IF filters, and only one variable coil and varicap diode.
The IC has an FLL (Frequency-Locked-Loop) system with an intermediate frequency of 70 kHz. The IF selectivity is obtained by active RC filters. The only function which needs alignment is the resonant circuit for the oscillator, thus selecting the reception frequency.
Spurious reception is avoided by means of using a muting circuit similar to squelch. This eliminates and rejects other input signals around selected frequency so that even remote stations can sound clear just as if they were located near by.
TDA7000’s audio output signal is only around 70mV which might be enough for driving crystal earphones or high impedance headphones. For higher power audio signal you can easily connect audio amplifier built around LM386 or just about any amplifier chip that will suit your taste.
Read more: TDA7000 FM Receiver / TV Tuner / Aircraft Receiver