This circuit is from a 1969 RE Experimenters Handbook. The circuit is powered by the voltage of the circuit being tested. Integrated circuits are current.
This experimental amplifier was found in the 1960 Mullard transistor reference manual. The...
This circuit from Motorola is from 1968, appearing elsewhere on this site. The transistors admit...
This circuit triggers the LED when the monitored battery voltage drops below 9 V for 12 V...