Figuring out what this circuit does
This is an AM radio demodulator. The L1 of RF transformer along with Cvar1 adjust the tuning frequency of incoming RF signal. The diode and C3 and R2 together form an &quot;envelope detector&quot; which extracts the envelope of the RF signal (u can google for envelope detector). The first OPAMP is just a buffer with a gain of 1. The next two opamps amplify the demodulated signal. why two opamp? because of bandwidth limitation of opamps. The last amplifier is a special amplifier for audio signal and can drive a little speaker.