A Pulse Slicer is a variation of the Zero Crossing Detector and is used to detect the zero crossings on an input signal with a varying baseline level. This circuit works best with symmetrical waveforms. The RC network of R1 and C1 establishes an mean reference voltage VREF, which tracks the mean amplitude of the VIN signal. The noninverting input is directly connected to VREF through R2. R2 and R3 are used to produce hysteresis to keep transitions free of spurious toggles. The time constant is a tradeoff between long-term symmetry and response time to changes in amplitude.
If the waveform is data, it is recommended that the data be encoded in NRZ (Non-Return to Zero) format to maintain proper average baseline. Asymmetrical inputs may suffer from timing distortions caused by the changing VREF average voltage.
For this design, follow these design requirements:
Figure 8-19 shows the results of a 9600 baud data signal riding on a varying baseline.