LM565 FSK demodulator circuit design
A very simple FSK demodulator for the 2025 Hz and 2225 Hz can be designed using the LM565 which is a general purpose phase locked loops IC containing a stable, highly linear voltage controlled oscillator for low distortion FM demodulation, and a double balanced phase detector with good carrier suppression.
The VCO frequency is set with an external resistor and capacitor, and a tuning range of 10:1 can be obtained with the same capacitor.
As you can see in the circuit diagram , this FSK demodulator require extreme few external components .
Changing the loop filter components we can modify the FSK demodulator frequency .
This demodulator circuit needs to be powered from an external 12 volts DC power supply .