A protection circuit for electronic circuitry comprising at least three diodes connected in series in such a manner that an anode terminal of a first diode is connected to a cathode terminal of a second diode to form a ring. A first terminal is connected between diodes of a first pair of consecutive diodes of the ring. A second terminal is connected between diodes of a second pair of consecutive diodes of the ring. The position of the first terminal is fixed and position of the second terminal is selectable in such a manner that a pre-determined turn-on voltage of the at least three diodes is obtained.