This CMOS circuit for LED displays is from a Radio Electronics magazine from February 1989. The circuit has an enable pulse for storing the value shown on the display.
In this 2002 circuit, we have the activation when the reservoir is empty and shutdown when full....
This circuit was found in a 2001 documentation. It is a test of zener diodes that uses a voltmeter or...
The output current is of the order of 100 mA maximum, but the transistor used can be changed for...