A CMOS temperature sensor circuit

A supply voltage (V-DD) independent temperature sensor circuit, which can be realized by the optimum combination of three current modes of n-MOSFETs including the subthreshold current using the feedback scheme from the temperature dependent voltage (V-TD) Output to the gates of three n-MOSFETs, was proposed and fabricated by a standard 1.2 mu m n-well CMOS process. The circuit consists of only 17 MOSFETs without high resistors resulting in a small die area of 0.18 mm(2). The temperature coefficient TC of the sensor circuit can be controlled by the channel length ratio L-4/L-3 of two n-MOSFETs. The average temperature sensor voltage V-TS and its typical TC are 1.77 V at V-DD = 5.0 V (20 degrees C) and 5.1 mV/degrees C for V-DD = 5.0 +/- 1.0 V in the temperature range of -20-100 degrees C in case of L-4/L-3 = 9, respectively.