This circuit was found in a 1965 Electronic Design. Transistor Q2 must be load dependent. The circuit can be adjusted for currents from 1 to 10 A. The voltage drop is 3 V and the maximum voltage is 35 V.
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...