Semi-conductor thermal protection arrangement

A semi-conductor protection arrangement for use with class AB, B or C power amplifiers or in any other circuit configuration wherein a reduction in drive signal at a stage prior to that of the protected semi-conductor results in a lessening of the protected semi-conductor dissipation, said arrangement comprising a temperature sensor thermally coupled with the protected semi-conductor for detecting the absolute temperature of the semi-conductor and electrically connected so as to reduce the drive signal of the semi-conductor when the temperature of said semi-conductor exceeds a predetermined temperature above the normal operating temperature of the semi-conductor, said temperature sensor being made of a material which satisfies the following criteria:

• (a) contains elements whose atoms when in chemical combination with other elements have an incompletely filled d-shell or an incompletely filled f-shell;
• (b) contains a substance effective to remove s- and p- electrons from the conduction bands of such atoms;
• (c) exhibits a sharp drop in its resistance-temperature characteristic at the above predetermined temperature;
• and (d) possesses a sufficient predetermined amount of temperature hysteresis, so that the temperature sensor reacts quickly to an increase in temperature above said predetermined temperature but reacts at a slower rate for minor temperature excursions in the transition region thus preventing thermal oscillation of the semi-conductor protection arrangement within the transition region.