This circuit indicates when the voltage of a 12 V battery is low. With changes, for example, the zener, the circuit can be used to monitor other voltages.
The integrated circuit used in this National Semiconductor project is not the most common and the...
In the figure we have the circuit of an amplifier for alternating signals with 10 times gain,...
I got this circuit from Hands-On Electronics, 1988. The American magazine no longer exists, but...