This 4-transistor amplifier can work from 4.5 or 6 V power supplies. We found it in a Mullard transistors manual from 1960. The transistors are from the time.
This circuit was obtained from an American 80's documentation. The operational ones can be...
This audio amplifier from the 70's uses a high voltage transistor. The transistors are from the...
This circuit can be found elsewhere on this site as part of alarms or sirens. The circuit given is...