A method for converting an analog signal (TP[i]), e.g. a voltage readout signal of a thermopile pixel or a pixel of another detector sensitive to radiation, into a multibit digital signal, comprising the following steps: - successively supplying analog signals (TP[i]) of different sizes to the input of a delta sigma converter for the duration of respective readout intervals within which the analog signals (TP[i]) each substantially remain unchanged, - forming a multibit digital signal corresponding to an analog signal by the delta sigma converter with a one-bit analog-to-digital converter in the form of a quantizer and a controller (ADCFB) connected in series thereto at whose output the multibit digital signal is available, - converting the multibit digital signal by a multibit digital-to-analog-converter into an analog feedback signal, - forming a differential signal from the analog signal (TP[i]) and the analog feedback signal, - multiplying said differential signal by a chopper signal having a first frequency in order to form a first differential signal, - multiplying said first differential signal by a second chopper signal having a second frequency in order to form a second differential signal, the second frequency being larger than the first frequency, - amplifying said second differential signal to form a third differential signal, - multiplying said third differential signal by the second chopper signal to form a fourth differential signal, - low-pass filtering said fourth differential signal by means of a low-pass filter (C1, C2) and supplying said low-pass filtered fourth differential signal to the input of the quantizer; - outputting a fifth differential signal by the quantizer; - multiplying said fifth differential signal by an inverted first chopper signal to form a sixth digital signal, - supplying said sixth digital signal to the controller (ADCFB) to form the multibit digital signal; and - outputting the multibit digital signal, optionally after digital filtering, - wherein the controller (ADCFB) is selectively operated in a first mode and in a second mode, - wherein the controller (ADCFB) compensates target value/actual value deviations between the analog signal (TP[i]) and the analog feedback signal faster in its first operating mode than in its second operating mode, - wherein the controller (ADCFB) is operated in its first operating mode in an initial phase of the readout interval for the purpose of tracking the digital multibit signal to the analog signal as quickly as possible, and - wherein the controller (ADCFB) is operated in its second operating mode after said initial phase of the readout interval and for the remaining duration. - successively supplying analog signals (TP[i]) of different sizes to the input of a delta sigma converter for the duration of respective readout intervals within which the analog signals (TP[i]) each substantially remain unchanged, - forming a multibit digital signal corresponding to an analog signal by the delta sigma converter with a one-bit analog-to-digital converter in the form of a quantizer and a controller (ADCFB) connected in series thereto at whose output the multibit digital signal is available, - converting the multibit digital signal by a multibit digital-to-analog-converter into an analog feedback signal, - forming a differential signal from the analog signal (TP[i]) and the analog feedback signal, - multiplying said differential signal by a chopper signal having a first frequency in order to form a first differential signal, - multiplying said first differential signal by a second chopper signal having a second frequency in order to form a second differential signal, the second frequency being larger than the first frequency, - amplifying said second differential signal to form a third differential signal, - multiplying said third differential signal by the second chopper signal to form a fourth differential signal, - low-pass filtering said fourth differential signal by means of a low-pass filter (C1, C2) and supplying said low-pass filtered fourth differential signal to the input of the quantizer; - outputting a fifth differential signal by the quantizer; - multiplying said fifth differential signal by an inverted first chopper signal to form a sixth digital signal, - supplying said sixth digital signal to the controller (ADCFB) to form the multibit digital signal; and - outputting the multibit digital signal, optionally after digital filtering, - wherein the controller (ADCFB) is selectively operated in a first mode and in a second mode, - wherein the controller (ADCFB) compensates target value/actual value deviations between the analog signal (TP[i]) and the analog feedback signal faster in its first operating mode than in its second operating mode, - wherein the controller (ADCFB) is operated in its first operating mode in an initial phase of the readout interval for the purpose of tracking the digital multibit signal to the analog signal as quickly as possible, and - wherein the controller (ADCFB) is operated in its second operating mode after said initial phase of the readout interval and for the remaining duration.