This 1000: 1 voltage-controlled filter circuit was found in an Electronics Today International in a 1980s edition. The circuit is based on components of the time.
The circuit presented may use any general purpose transistor. The indicator is an LED and...
The circuit shown uses the LM324, but can be implemented with other operational ones. The source...
This circuit was obtained from an English publication from the 70's. The circuit is still current for...