E)
We found this circuit in a PE Hobbyst Handbook from the 90s. The components are common, except the Geiger tube. The transformer is also a component that requires care when choosing.
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...