This circuit was originally designed to measure capacitance with an ICL7107 but can be used with other digital modules. The circuit is from Electronics Now magazine from November 1996.
This circuit that draws 1 out of 8 LEDs was found in an 80's American documentation. The circuit...
This protective circuit for power lines was found in a Radio Electronics from November 1957. The...
In figures 1 and 2 we have two current drains that can be made with operational amplifiers and...