A Constant-Fraction Discriminator for Sub-Nanosecond Timing
1 min read
Summary
A constant-fraction discriminator, as its name suggests, triggers at a constant fraction of the signal pulse, which avoids the time-walk effect that results from using a voltage threshold.
However, these circuits tend to be expensive due to the need for very fast operational amplifiers.
Engineer Michael Wiebusch has created a cheaper alternative using cheap integrated circuits and transistors, eliminating the need for op-amps, and has published a hacker-friendly implementation of the design.
The prototype was designed for a gamma-ray spectrometer, but the basic design could be adapted for different pulse signals.
The only downside is that the circuit has to be designed for a specific pulse length, and this prototype has a timing deviation of just 60 picoseconds, giving it high precision.
