Power switches

A switching device suitable for operation in temperatures over 150{ C comprises first (1) and second (2) transistors, the drain 1D of the first transistor being connected to the source (2S) of the second transistor, the gate (2G) of the second transistor being connected to the source (1S) of the first transistor and the gate (1G) of the first transistor being connected in use to control circuitry (3) such that current flow through the transistors is controlled in use by the application of a control signal from the control circuitry, characterised in that the first and second transistors are both operative at temperatures over 150{ C.