This is a circuit suggested by Linear Technology in a 1980s documentation. The integrated circuit is from the era. Observe the input and output voltage.
This circuit was found in an old publication from 1989 but can still be assembled today with BD135...
We found this circuit in a 1987 documentation. Its purpose is to turn on a garage light using the...
In the figure we have a simple logic level indicator for TTL circuits or powered by 5 V....