The Programmable Analog Circuitry of the CDF Trigger

A flexible trigger has been partially built to trigger the CDF, Colliding Detector at Fermilab. A programmable analog system can yield a large dynamic range of outputs. With suitable management it will control noise to achieve the high resolution and fast process necessary for such a trigger. The first level output will be delivered in three microseconds after a beam crossing. The system is designed to have a resolution of one part in one thousand. Analog processing, where just summing is involved, can handle many channels faster than an equivalent digital processor exhibiting the same resolution. As a result, this system will be much simpler with far less coinponents. Digital intervention controls channel gain and bias. It also sets a comparison level, and includes or excludes individual channels in the various output summing networks that will determine the trigger result. The results of the analog processing which are input to the digital control include the value of the channel magnitude comparison, the sign of the results of the various sums and finally the fast flash analog to digital converter output values. A set of DACS are used to control the pedestal of the respective various sum networks.