We found this circuit in an English publication from the 60's. The transistors are of germanium of the time and the headphones must be high impedance magnetic.
The circuit shown in the figure serves as a pre-amplifier with a voltage gain of around 12 times,...
Based on Texas Instruments documentation, this circuit serves for sensor interfacing. The circuit is...
This article is from a publication by A. Fanzeres from the 70s. We kept the original text. This...