This circuit was found in a 1967 Electronic Design. The FET is from that time. Capacitor C is determined by the frequency of the signal worked.
Using the 2N2646 this circuit was found in a Radio Electronics magazine from July 1968. The...
The purpose of this circuit found in a 1990s Popular Electronics is to increase the current...
Found a documentation for PC from 1992, this circuit is indicated for the English power grid of...