Evoked Response Signal and System Nonlinearity

The evoked response potential measurement system can include nonlinear elements. These can arise due to such operations as limiting in the amplifier or A/D converter. Nonlinear operations on the data will give rise to changes in the measured evoked potential. This paper investigates the effects of the limiter and comparator nonlinearities on evoked potential signal distortion, signal-to-noise ratio, and amplitude resolution. It is shown that, for input signal-to-noise ratio less than one, the distortion and signal-to-noise ratio degradation are small while an improvement in resolution is obtained. Of particular interest is the result that the comparator can replace the A/D converter with the advantages of improved resolution and processing time at little cost in distortion or signal-to-noise ratio degradation. The theoretical results are verified by measurement simulation.