AMPLEX, a low-noise, low-power analog CMOS signal processor for multi-element silicon particle detectors

AMPLEX is a monolithic analog signal processor fabricated in 3 μm n-well CMOS and originally designed for the inner silicon detector of the UA2 Experiment at the CERN SPS Collider. However, it is suitable for various other types of detectors, and results are also given for a multiwire proportional chamber (MWPC). The chip contains 16 channels, each consisting of a charge amplifier, a sharper amplifier and a track-and-hold stage. The channel outputs are connected to an analog multiplexer which is controlled by digital circuitry. For a power consumptin of 1 mW per channel and an adjustable peaking time of 600 to 800 ns, the equivalent noise charge is 400 rms electrons plus 33 rms electrons per pF of input capacitance. The DC stabilisation of the charge amplifier is obtained using a non-linear feedback resistor. This novel MOS element is a key feature of the design and enables low noise as well as DC stability of the charge amplifier, even for increased detector leakage current up to several hundred nA. Such operating conditions can occur following radiation damage of silicon pad detectors. (orig.)