A demodulating circuit includes a differentiating circuit that outputs a differentiated
signal indicating voltage changes at rising and falling edges of a received pulse
signal, and a hysteresis comparator that compares the differentiated signal with
upper and lower threshold voltages, thereby generating a demodulated logic-level
signal. The differentiating circuit can rapidly track variations in the direct-current
offset of the received pulse signal. Positive feedback can enable the hysteresis
comparator to maintain the correct output logic level during runs of 0's or 1's
of arbitrary length in the received pulse signal. The demodulating circuit consumes
comparatively little power, and is particularly useful for receiving signals transmitted
in bursts.
