Abstract: The present invention provides a two-terminal, transistor-PTC, circuit protection device that has a reduced size and weight and is particularly suitable for use, for example, in portable electronic devices and high density electronic circuits. According to one embodiment of the present invention, a circuit protection device comprises a positive coefficient temperature (PTC) element and a bipolar transistor having base, collector, and emitter terminals. The PTC element is connected between the base and collector terminals of the transistor. The PTC element may be thermally coupled to the transistor and packaged with the transistor as a hybrid device. An electrical load may be connected to the collector terminal of the transistor. According to another embodiment of the present invention, a circuit protection device comprises a PTC element and a Darlington circuit having base, collector and emitter terminals. The PTC element is connected between the base and collector terminals of the Darlington circuit.

Abstract: A circuit protection device for protecting an electrical load includes a three-terminal switch element such as a bipolar, or junction or metal-oxide-semiconductor field effect, transistor and a positive temperature compensation (PTC) resistor. In several embodiments the PTC resistor is in series with the current-carrying electrodes of the transistor. In other embodiments the PTC resistor, or a second PTC resistor, is connected to a control element of the transistor. Both DC and AC load-protection circuits are described.