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.

Precision Diode LM101 (CB4607E)
The basis of this circuit is a National Semiconductor operational amplifier that functions as a...
4mA at 20 mA Generator XTR115 and PGA309 (CB15571E)
The presented circuit is suggested by Texas Instruments (www.ti.com) in its Application Report...
Timer 555 (CB8111E)
Found in a PE Hobbyst Handbook of 1991, this circuit was originally proposed to time photographic...