Discrete Transistor VCA

A Voltage-Controlled Amplifier (VCA) made from three BC549 NPN transistors and three BC214 PNP transistors. It's a Gm Cell with variable current followed by a simple op-amp.

 

The input is rigged up to an HP 4204A Oscillator with a 3310A Function Generator supplying the modulation signal. Output goes to a Tek 5440 analog oscilloscope and an X-Mini capsule speaker.

Done