CMOS preamplifier with high linearity and ultra low noise for X-ray spectroscopy

We present an ultra low noise charge preamplifier suitable for small capacitance (200 fF), low leakage current solid state detectors. A self adaptive bias circuit for the MOS feedback device establishes the static feedback resistance in the G/spl Omega/ range while tracking the threshold variations and power supply and temperature fluctuations. The linearity of the gain versus input charge has been improved by means of a voltage divider between the output of the charge-sensitive amplifier and the source of the feedback transistor. With the preamplifier alone, we measure a room-temperature equivalent noise charge (ENC) of 9 e/sup -/ rms at 12 usec shaping time. When coupled to a cooled detector a FWHM of 130 eV is obtained at 2.4 usec shaping, corresponding to an ENC of 16 e/sup -/ rms. This is the best reported resolution obtained with a CMOS preamplifier. The circuit has good linearity (<0.2%) up to 1.8 fC. Since the preamplifier's ENC is limited by flicker noise, we fabricated the circuit in two 1.2 /spl mu/m CMOS technologies. Device measurements allow us to compare the 1/f noise behavior of each foundry. In addition to the preamplifiers, a 1 us shaper and a 50 /spl Omega/ output driver are included on the die.

[1]  Pierre Jarron,et al.  Amplex, a low-noise, low-power analog CMOS signal processor for multi-element silicon particle detectors , 1990 .

[2]  S. Berman,et al.  Nuovo Cimento , 1983 .

[3]  Heike Soltau,et al.  Silicon drift detectors for high resolution room temperature X-ray spectroscopy , 1996 .

[4]  Veljko Radeka,et al.  LOW-NOISE TECHNIQUES IN DETECTORS , 1988 .

[5]  I. Kipnis,et al.  XPS: a multi-channel preamplifier-shaper IC for X-ray spectroscopy , 1997 .

[6]  Marco Sampietro,et al.  Optimum filters for detector charge measurements in presence of {1}/{f} noise , 1990 .

[7]  Paul O'Connor,et al.  CMOS preamplifier for low-capacitance detectors , 1997 .

[8]  Willy Sansen,et al.  Limits of low noise performance of detector readout front ends in CMOS technology , 1990 .

[9]  Marco Sampietro,et al.  Advanced experimental application of a digital signal processor in high resolution x‐ray spectroscopy , 1995 .

[10]  P. Rehak,et al.  Signal Shaping and Tail Cancellation for Gas Proportional Detectors at High Counting Rates , 1980, IEEE Transactions on Nuclear Science.

[11]  Willy M. C. Sansen,et al.  Low-noise wide-band amplifiers in bipolar and CMOS technologies , 1990, The Kluwer international series in engineering and computer science.

[12]  Antonio Francesco Longoni,et al.  Design of a charge sensitive preamplifier on high resistivity silicon , 1988 .

[13]  H. Kraner,et al.  Fabrication of large area Si cylindrical drift detectors , 1994 .

[14]  Helmuth Spieler,et al.  A high rate, low noise, X-ray silicon strip detector system , 1994 .