BACKGROUND

In the field of integrated circuits (ICs), a thermal sensor is typically used to detect a temperature of the IC, and a bandgap reference circuit is used to provide a stable and low temperature coefficient reference voltage. Both of the thermal sensor and the bandgap reference circuit use a PTAT (Proportional to absolute temperature) circuit to generate a PTAT signal. The PTAT circuit uses the electrical characteristics of the voltage difference between two base-emitter voltages, i.e. delta VBE, to generate the PTAT signal. However, the linearity of the PTAT signal in response to the absolute temperature deteriorates in advanced semiconductor technology. Therefore, a high linearity PTAT signal is highly desirable in the field of thermal sensor or bandgap reference circuit.

