Abstract: The digital sampler circuit processes an output signal from a high gain analog amplifier having as input an infrared motion detector output signal and a negative low pass filtered feedback signal. The amplifier output signal is a substantially square pulse signal having an irregular frequency and duty cycle and has an average duty cycle indicative of a DC level and a slow change in the DC level of the detector output signal. The sampler circuit includes a detector circuit for detecting the amplifier output signal and discriminating at regular intervals a high/low state of the output signal, and generates a high/low feedback signal corresponding to the high/low state of the output signal detected. The high/low state of the output signal is analyzed over a predetermined number of the intervals to obtain a ratio value for producing an output digital signal sample value. The digital sample value is a measure of the DC level and the change in the DC level of the detector output signal.