This circuit was found in the March 1997 Electronics Now magazine. It uses a common analog indicator and the transistor is a general purpose one.
We found this amplifier circuit for inductive audio pickups in a documentation from the 70s. The...
The circuit is from Motorola's Linear Databook from 1990, but the configuration is current because...
This 6-transistor commercial radio with 6 V supply was found in a Japanese publication from the...