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.

Immobilizer for car (CB26165E)
This circuit for cars with mechanical ignition systems was found in the Electronics Experimenter handbook...
Code Sidetone Generator (CB26323E)
This code practice circuit was found in a 1990s issue of Radio Amaterur Today magazine. It...
ADC interface with Z80 Using ADC0808 (CB14350E)
The circuit presented was found in the Linear Applications Handbook of the National Semiconductoir of 1994....