Henk ten Pierick wrote: > Hi Don, > > Any comparator or slicer has a noise density and a noise bandwidth. > The noise value of this slicer is the integral of the noise density > over the noise bandwidth. The noise bandwidth is the slicer > bandwidth, not the slicer frequency. Due to the slope, thus the slew > rate, of the input signal the input noise is converted to jitter. > Which is why when the input slope (slew rate) is low (< 1E6 V/s or so. The exact limit depends on the noise and noise bandwidth of the comparator), it is advantageous to amplify the slope using a chain of amplifiers of where the gain and bandwidth increases for each successive stage. The output of the slope amplifier then drives the comparator/slicer/zerocrossing detector. The optimum sequence of gains and bandwidths depends on the noise on the input signal and the noise characteristics of each amplifier stage. The disadvantage of such circuits is the accompanying phase shift and associated tempco due to the low pass filter components used in each stage. > Henk > Bruce
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