TEMPERATURE RESPONSIVE CIRCUIT FOR PROTECTING AN ELECTRON DEVICE

The protection circuit for an electron device includes a silicon controlled rectifier (SCR) selectively triggered by a voltage divider including first and second thermistors. The first thermistor monitors the temperature of a heat sink which is thermally connected with the device, and the second thermistor monitors the ambient temperature. When the sink and ambient temperatures indicate the device is about to overheat, the divider provides a voltage which triggers the SCR to change the bias thereby decreasing the power level of the device. The temperature of the device decreases in response to the decrease in power level. The protection circuit can be used with the power amplifier of a radio transmitter wherein the energizing circuit of the SCR is broken each time the transmitter is keyed to reset the protection circuit.