Using the TDA7021T integrated radio receiver circuit can be designed a very simple high efficiency portable radio receiver circuit fully compatible for applications using the low-voltage micro tuning system (MTS). The TDA7021T has a frequency locked loop (FLL) system with an intermediate frequency of 76 kHz. The selectivity is obtained by active RC filters. The only function to be tuned is the resonant frequency of the oscillator.
Because of the low intermediate frequency, low pass filtering of the MUX signal is required to avoid noise when receiving stereo. 50 kHz roll-off compensation is needed because of the low pass characteristic of the FLL.
For mono application this amplifier can be used to directly drive an earphone. The field-strength detector enables field-strength dependent channel separation control.
With a combination of a low voltage PLL stereo decoder ( TDA7040T ) and a low voltage mono/stereo power amplifier we can build a simple portable radio .
For this radio receiver circuit we need a 5V dc power supply .
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