This circuit is a four-quadrant multiplier using an LM3900. The circuit was found in the July 1988 Radio Electronics magazine.
This circuit is from 1999 documentation. However, it can still be easily assembled, as all...
This circuit, obtained from the component manual used, has an ultra narrow 1 kHz range given by...
The zener diode determines the triggering of the circuit and R3 must be a resistor that will be...