TRIPLEX: an amplification and trigger chip for a Si-strip microvertex detector

The TRIPLEX, a 128 channel integrated circuit, intended for use with the DELPHI Si-strip microvertex detector is described. It includes a sensitive differential discriminator per channel for participation in the DELPHI trigger. The discriminators, which compare sampled signals from before and after beam crossing, are servo-stabilized between beam crossings to provide uniform thresholds. The preamplifier noise (90 electrons+8 electrons per pF for a 1.5 microsecond peaking time) is compatible with a trigger threshold of less than 1/4 MIP. The 128 discriminator outputs are connected in wired-OR to the trigger output. An automatic mechanism is included to disconnect noisy channels from the trigger