A preamplifier-shaper-stretcher Integrated Circuit system for use with gernanium strip detectors

A 16-channel integrated Circuit readout electronics chip is being developed for use with a germanium strip detector. Such a system will provide superi or energy resolution with 2-dimensional imaging in a single instrument that can be used for X-ray imaging and nuclear line gamma-ray spectroscopy. As part of the total ASIC development, prototype ICs of a typical channel have been designed, fabricated and tested. These integrated circuits include a low-noise, variable gain, preamplifier circuit that can detect both positiv e and negative going input charges, a 4-pole pulse shaper with variable pea king times and a stretcher circuit that can do a peak detect and hold for t he different peaking times. The integrated circuits are fabricated in a 1.2 micron n-well CMOS process. The noise performance for this system was meas ured to be 185erms +14e/pF for a 2 mus peaking time and gain at similar to 200mV/fC. Linearity measurements in both inverting and non-inverting modes of operation were approximately +/-1%. Peaking times from 0.5 microseconds to 8 microseconds and gain adjustments to get up to 400mV/fC per channel we re done through digital switching.