This circuit was obtained in a Motorola documentation from 1968. The circuit uses a power transistor of the time. Modern equivalents according to the load current and voltage can be used.
This is an old test circuit for integrated TTL counters, feeding a Nixie tube, common at the time....
This traditional crystal radio circuit, but which has a modern version with diode, was found in an...
This headphone amplifier using a pickup coil can be used as an extension for devices such as TVs,...