A CMOS Temperature Sensor Using Cascoded PNP Transistors

In this paper, a CMOS temperature sensor using cascaded PNP transistors was designed and measured. The commonly used band gap reference current source, which used bipolar junction transistors (BJTs) to implement output current components with negative and positive temperature coefficients, was adopted to generate a temperature-insensitive reference current source. The base-emitter voltage (V_EB), i.e. output voltage, of a PNP BJT under a constant collector biasing current demonstrates a negative temperature coefficient. To enhance sensitivity of transfer characteristics of the output voltage versus temperature, two PNP BJTs under a constant collector biasing current were arranged into a Darlington-pair topology and were used as a temperature sensor. Temperature sensor has the sensitivity of -3.93 mV/°C with the temperature error of ±0.6°C or so for the calibrated temperature ranging from -15°C to 110°C.