This circuit has an automatic dynamic gain control in a range of 6 dB to 40 dB. We found it in documentation from the 90s. The bipolar transistor is a general purpose type.
In this circuit of a 1968 publication the unijunction may be 2N2646 and the transistor BC548. The...
The purpose of this circuit is to improve a trigger circuit using a zener diode. The circuit was...
This interesting circuit of the American publication Electronics Handbook Volume XIII 1993 shows a...