P. Oconnor et al., ULTRA-LOW NOISE CMOS PREAMPLIFIER-SHAPER FOR X-RAY SPECTROSCOPY, Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 409(1-3), 1998, pp. 315-321
We report here an Ultra Low Noise CMOS charge-sensitive amplifier (CSA
) and a CSA-Shaper for X-ray spectroscopy, suitable for a small anode
capacitance, low leakage current solid state detector. The continuousl
y sensitive CSA and CSA-Shaper use a MOS transistor MF to discharge th
e integration capacitance; a novel self-bias circuit biases MF in the
G Ohm region (subthreshold region) while tracking process, temperature
and supply voltage variations. A T-Network in the DC-feedback improve
s the CSA gain linearity (within 0.1% up to 1.8 fC input charge). The
CSA-Shaper features a novel Adaptive Pole-Zero cancellation scheme: th
e Zero in the Shaper adapts itself statically and dynamically to cance
l the CSA Pole. The noise performance of the CSA has been measured: wi
th no detector connected and MF pinched, the room-temperature equivale
nt noise charge (ENC) is 9e rms at 12 mu s shaping time. When connecte
d to a cooled detector (T = - 75 degrees C), with MF in pinch off, an
ENC of 13e rms is achieved (FHWM = 111 eV) at 2.4 mu s shaping time. T
his is the best reported energy resolution ever obtained with a CMOS p
reamplifier. (C) 1998 Elsevier Science B.V. All rights reserved.