Signal amplitude comparator

A signal amplitude comparator configured to receive an input signal, a first reference input signal and a second reference input signal and is configured to generate an output which indicates whether the input signal exceeds a pre-determined threshold value, said signal amplitude comparator comprising a first differential input circuit that is biased, is configured to receive the input signal, and is configured to generate a first output that is a non-linear function of the input signal, a second differential input circuit which is biased similarly to the first differential input circuit, is configured to receive said first reference input signal, and is configured to generate a second output that generally tracks process, temperature and supply variation, a pair of linear input amplifiers which are connected to the first and second differential input circuits and are configured to receive and translate the input signal and the first reference input signal to levels suitable for the first and second differential input circuits, an amplifier which is connected to the first and second differential input circuits, a filter which is connected to the amplifier, and a comparator which is connected to the filter, said comparator configured to receive an output from the filter and the second reference input signal, said amplifier configured to amplify a signal difference between the first and second outputs and configured to output a train of pulses to the filter if a peak of the input signal exceeds the first reference input signal, said comparator configured to compare the first and second outputs and generate the output which indicates whether said input signal exceeds the pre-determined threshold value.