Fast ADC Input Waveform "Shaping"
The shaping amplifier preceeding the fast ADC distorts the signal so
that a minimum of information is lost. The shaping allows the
collection of several ADC samples on the rising, and trailing edge of
the resultant pulse. If the input signal were undistorted, it
would only be possible to sample an single photoelectron waveform once.
The gain implemented in the stages also serves to match the
amplitude of the signal to the desired number of ADC counts.
E1, E4, and E4, obviously, are actually op-amps.
The circuit is DC coupled from input to output, so it tracks changes in
the pedestal level used by the ATWD signal handling path.
G. Przybylski May 12, 2003