This simple audio and RF signal tracker was found in a Japanese publication in 1967. The transistors are made of germanium and the headphone is made of crystal.
This circuit is from the 1990 Motorola Linear Databook. The integrated circuit used is the LF355,...
This high impedance amplifier is from 1985 documentation by General Electronic. The amplifier with...
Based on the TCA6600 or TCA5500 this circuit was found in a 90’s European documentation. The...