A non-delayed input signal is provided to a first comparator input and, a delayed input signal is applied to a second comparator input. An offset voltage is applied between the delayed and non-delayed signals at the comparator inputs. When an input pulse appears on the input signal, the non-delayed input signal will rise immediately and maintain itself more positive than the delayed input, keeping the comparator output inactive. As long as the input signal is rising, the comparator output is maintained low, or inactive. When the non-delayed signal reaches its peak and turns downward, the delayed input signal is still rising and crosses over the first pulse, creating a change of state at the comparator output to a high or active state. The signal edge resulting from this change of start represents initial detection of an input pulse. The time of occurrence of this detection edge is substantially independent of the pulse amplitude. To extend the dynamic range of the pulse discriminator, multiple channels, each implemented to handle a distinct range of signal levels, may be included, and combined at their outputs. To improve accuracy for very low-level signals, and to reduce the incidence of false alarms, a separate detection threshold can be used to gate the comparator.
