Found in a Popular Electronics from the 90s, this circuit presents the difficulty of obtaining the Geiger Tube. The other components are common, admitting equivalents.
This circuit is from an English magazine of 1977. The circuit is still current, just using BC547...
The adjustment of the maximum load voltage is made in the trimpot. The circuit is from 1994...
In the figure we have the conventional configuration of a differential amplifier with the...