TDA7021T

* RF input stage
* Mixer
* Local oscillator
* IF amplifier/limiter
* Frequency detector
* Mute circuit
* MTS compatible

* Loop amplifier
* Internal reference circuit
* LF amplifier for
- mono earphone amplifier or
- MUX filter
* Field-strength dependent channel separation control
facility

The TDA7021T integrated radio receiver circuit is for portable radios, stereo as well as mono, where a minimum of
periphery is important in terms of small dimensions and low cost. TDA7021T is fully compatible for applications using the
low-voltage micro tuning system (MTS). The IC 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 of TDA7021T to be tuned is the resonant frequency of the
oscillator. Interstation noise as well as noise from receiving weak signals is reduced by a correlation mute system.

Special precautions of TDA7021T have been taken to meet local oscillator radiation requirements. 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, needed because of the low pass characteristic of the FLL, is performed by the integrated LF amplifier.
For mono application this amplifier TDA7021T can be used to directly drive an earphone. The field-strength detector enables
field-strength dependent channel separation control.