Undervoltage detector with the LM3900 (CB25172E)

The figure shows how to implement an undervoltage detector using a Norton amplifier and a zener diode as the main elements.

Battery Indicator (CB15925E)
This indicator, shown in the figure and suggested by National Semiconductor, causes an LED to...
Two Tone Alarm (CB18462E)
This traditional two-tone alarm configuration with the 4011 integrated circuit was found in a 1998...
Infinite Impedance (CB6154E)
This circuit is from an American 1967 documentation and can be implemented with modern equivalent...