This simple tester was found in a Popular Electronics from the 90s. The circuit is powered by two 9 V batteries since it requires a symmetrical source.
We found this circuit in a 1965 publication by General Electric. The zener is 8.2 V x 1 W and the...
This circuit was found in a 1994 documentation. The transistors can be BC558 and BC548 and the...
This amplifier stage, obtained in a 1980 publication, has a low input impedance and a high output...