A semiconductor device for measuring IR radiation comprising: at least one sensor pixel; at least one reference pixel shielded from said IR radiation comprising a heater; a controller adapted for: measuring a responsivity by applying power to the heater, while not heating the sensor pixel; measuring a first output signal of an unheated pixel and a first reference output signal of the heated pixel, obtaining the responsivity as a function of a measure of the applied power to the heater and of the difference between the first output signal and the first reference output signal; applying a period of cooling down until the temperature of the reference pixel and the sensor pixel are substantially the same; generating the output signal indicative of the IR radiation, based on the difference between the sensor and the reference output signal, by converting this difference using the responsivity.