Low-noise multirate SC read-out circuitry for thermoelectric integrated infrared sensors

In this paper we present a switched-capacitor multirate read-out circuit for integrated thermoelectric infrared sensors. The target application is a passive intrusion detector. The signal generated by the sensor in this particular case is quite small (few tens of μV) and has a narrow bandwidth (0.1÷10 Hz). It must be amplified (keeping the noise level as low as possible) and filtered. The proposed solution consists of an auto-zeroed low-noise transconductance stage followed by a multirate switched-capacitor integrator. The transconductor transforms the sensor output voltage in a current which is then processed by the integrator. The proposed circuit and the infrared sensor were integrated in a 1.2 μm industrial CMOS technology. Simulations and experimental measurements on the integrated prototype demonstrate the validity of the proposed approach