AC voltage probe (CB8185E)

This circuit for voltages up to about 20 V was found in a 90s Popular Electronics. The LED can be of any type or color.

VU Meter LM381 (CB19613E)
The LM381 integrated circuit is not very common today. The circuit is from an old publication, but it can be...
Audio Expander (CB25560E)
This circuit is based on the TDA3810N. We found it in the March 1992 issue of Radio Electronics magazine....
Fast adder 2 (CB7056E)
This is another quick adder that we found in an Electronic Design from the 80s. It also applies to...