This circuit was found in a Popular Electronics from the 90s. It is intended to power the filament of old radio valves in recovery works. It is indicated for tubes that use 5 V of filament.
We found this circuit in an old documentation from the 70s. The text is the original one of the...
The circuit shown in figure is suggested by Maxim in an application note. The operational...
We found this amplifier in a 1990 documentation. The transistors are common, having been made...