In accordance with an embodiment, a proportional to absolute temperature (PTAT) circuit includes a first bipolar transistor having a collector coupled to a common node; a second bipolar transistor having a collector coupled to the common node; a MOSFET having a load path coupled between a base of the first bipolar transistor and a base of the second bipolar transistor; and an amplifier having a first input coupled to an emitter of the first bipolar transistor, a second input coupled to an emitter of the second bipolar transistor and an output coupled to a gate of the MOSFET.