This circuit was published in an article in Electronics Now magazine in October 1995. The circuit includes a power supply. The power transistors are equivalent.
This circuit is from the 1972 Linear Data Book of RCA, but it can be made with more modern...
I found this simple circuit from an English magazine from 1984. The circuit can be easily...
We found this logic level tester in a 1976 documentation. The circuit is powered by the voltage of the...