This circuit was found in the July 1994 issue of Electronics Now magazine. The relay can be rated at up to 12 V and 100 mA. The transistor is a general purpose transistor.
The circuit in the figure is based on two integrated LM108 and its gain is basically determined by the...
Found in a 1968 Ferranti documentation, this circuit can be implemented with modern equivalent...
This amplifier stage was equipped with a Motorola radio from the 70s. The transistors were from...