Found in a 1980s telecommunications documentation, the circuit presented acts as a product detector. The modulator or mixer in the square may be that of the previous circuit.
We found this test circuit in Radio Electronics magazine from July 1962. The circuit uses...
We found this circuit in an American publication from the 1980s. Equivalent modern operational amplifiers...
The transistors in this circuit can be the BC548. Capacitors determine the frequency and can be...