Abstract: Protection circuits (1) to be located between power supplies (2) and further circuitries (20,30) for protecting further circuitries (20,30) against voltage irregularities and comprising main transistors (7) coupled to switching circuits (10) for rendering main transistors (7) operative/non-operative can be made more allround by providing them with comparators (11) for controlling gate voltages of main transistors (7) via switches (12,13) to get protection against small negative voltage pulses and voltage fluctuations. Said switches (12,13) comprise two switches (12,13) for interrupting a reference voltage generated by a reference voltage source and for supplying a nearby ground voltage to said gate. A diode (14) between switch (13) and gate allows negative voltages at said gate for simplifying the introduction of further stages. Thick oxide transistors (15) protect further circuitries (20,30) and main transistors (7) against large negative voltage pulses.

Abstract: Protection circuits (1) to be located between power supplies (2) and further circuitries (20,30) for protecting further circuitries (20,30) against voltage irregularities and comprising main transistors (7) coupled to switching circuits (10) for rendering main transistors (7) operative/non-operative can be made more allround by providing them with comparators (11) for controlling gate voltages of main transistors (7) via switches (12,13) to get protection against small negative voltage pulses and voltage fluctuations. Said switches (12,13) comprise two switches (12,13) for interrupting a reference voltage generated by a reference voltage source and for supplying a nearby ground voltage to said gate. A diode (14) between switch (13) and gate allows negative voltages at said gate for simplifying the introduction of further stages. Thick oxide transistors (15) protect further circuitries (20,30) and main transistors (7) against large negative voltage pulses.