This circuit for musical instruments was found in a 90’s Elektor. The circuit still applies, as the components used can still be obtained with some ease.
Found in Linear Technology documentation from the 90s, this circuit uses an operational amplifier...
This simple circuit that interrupts the supply of a 12 V load in the event of an overvoltage was found in...
The circuit shown is from National Semiconductor, having been found in the 1994 Linear Application...