In this paper, we investigate the noise characteristics of a low-voltage CMOS temperature sensor, designed in a CMOS standard process (Alcatel Mietec 0.7 #mu#), which makes use of a temperature sensitive Wheatstone bridge and of a differential amplifier. The bridge is fabricated using polysilicon resistors layers of positive and negative first order temperature coefficients to realize opposite resistors. The differential amplifier, formed by a low supply voltage (1.5 V) low noise CMOS OTA and four external resistances, improves the circuit sensitivity to about 20 mV/deg C. The total circuit resolution is 10~(-2) C.
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