We found this circuit in the Linear Applications Handbook by National Semiconductor. It uses the LM3900, an operational transconductance amplifier as a base. Q1 can be a 2N2222 or similar.
The idea of this automation can be extended to other applications that involve the control of...
We found this source in a 1998 publication. It was originally intended for FM transmitters, but...
This circuit was published in a 90s Radio Electronics. The circuit uses the well-known LM386 that...