Found in American documentation from the 90's, this circuit can be implemented with modern equivalent components. Observe the symmetrical power supply.
In the figure we have the way to activate a red LED that needs 1.7 V or even others with higher...
This circuit was obtained in a 1979 publication, but it can be assembled with the BD135 instead of the...
Found in Radio Electronics from the 90's, this circuit employs a 3140 operational amplifier, still...