This very complex circuit in terms of the number of transistors was found in Radio Electronics from March 1966. The circuit is for low impedance headphones. The transistors are from the time.
This configuration uses the 4 gates of a 7401 integrated circuit. The capacitors determine the...
This is a precision half-wave rectifier, suggested by Texas Instruments. Diodes are commonly used,...
This circuit is suggested by National Semiconductor in its 1994 Linear Applications Handbook. The...