Abstract: A temperature sensing circuit (100) for sensing the temperature of an active semiconductor device, for example, a power MOSFET (11) of a semiconductor body (10). The circuit has a first temperature sensing device (R1R2) provided on the semiconductor body at a first position (P.sub.1) adjacent a periphery (12) of the active semiconductor device (11), a second temperature sensing device (R3,R4) provided on the semiconductor body at a second position (P.sub.2) further from the periphery of the active semiconductor device than the first position. An arrangement, for example, a comparator responsive to the first and second temperature sensing devices provides a control signal to switch off the active semiconductor device (11) when the difference in the temperature sensed by the first and second sensing devices reaches a predetermined value.

Abstract: A circuit for measuring the current through a power transistor comprising at least two groups of parallel-switched transistors. A first large group of transistors carries the power current and a second group of transistors carries a current to be measured which is proportional to the power current when the base-emitter voltage or the gate-source voltage (in the case of bipolar or field effect transistors) of all the transistors in the groups is the same. The voltage difference between the parallel-switched emitters or sources of the two groups is measured by means of a differential amplifier and the emitter or source voltage of the first group is impressed on the emitters or sources of the second group by means of a control transistor driven by the differential amplifier. Except in extreme cases (for example, a short-circuit) the current to be measured through the second group follows the power current through the first group on a proportional basis.

Abstract: Low voltage semiconductor devices are integrated monolithically with a high voltage semiconductor device on an electrically conductive substrate. The substrate forms an electrode of the high voltage device and is connected in use to the high voltage terminal of a power supply. The low voltage devices operate from a regulated low voltage supply, which is regulated with reference to the high voltage supply voltage, and not with reference to ground. This reduces the need to isolate the low voltage devices from the conductive substrate. An intelligent power switch circuit constructed in accordance with the invention is suitable for use in automotive and lighting applications.