Using the 2N2646 this circuit was found in a Radio Electronics magazine from July 1968. The transistors are from the time and the lamp can be replaced by a high-power LED in a current version.
Based on 4066 CMOS, we found this circuit in a Popular Electronics from 1992. The signal is...
This circuit was used to regulate the speed of small DC motors of cassette recorders. However, if the...
The CUT frequency for this filter is determined by the capacitors. The µA4138 is a quad version of...