The purpose of this circuit is to reduce the ripple of a power supply. The circuit is from a Radio Electronics from March 1985. The transistor must have a capacitance according to the source.
This circuit was obtained from an American 80's documentation. The balanced mixer can be shown in...
This circuit was found in a 90s Electronic Engineering. The quadruple operational amplifier can be...
I found this circuit in an English publication from 1989. This configuration can be mounted with...