The circuit shown was found in the 1994 National Semiconductor's Linear Application Handbook. The op amp admits equivalents and the power supply must be symmetrical.
In the figure we have a variation of the previous circuit with only one transistor, using the...
We found this circuit in an American documentation from the 90s. Through an LED it indicates the...
This automotive grade circuit was found in a 1991 Electronics Hobbyist. The transistors are...