Low-noise CMOS preamplifier-shaper for silicon drift detectors

We have designed a 16-channel preamplifier-shaper for particle tracking using silicon drift detectors (SDD). The preamplifier, which is optimized for a detector capacitance of 0.2 - 0.8 pF, uses two new circuit techniques to achieve a low noise (ENC 120 e(-) + 62 e(-)/pF), high linearity (< 0.5% to 50 fC), and good tolerance to process variations and temperature and power supply fluctuations. The circuit is continuously sensitive, has no digital signals on chip, and requires no external components or critical adjustments. The peaking time of the shaper is 50 nsec and the power dissipation, including an off-chip driver, is 6.5 mW/channel. The circuit is fabricated in 1.2 mu m CMOS and can accomodate detector leakage currents of up to 1.5 uA. Although the circuit was developed for use with particle tracking detectors, these techniques are also well-suited for the design of lower-noise preamplifiers for high-resolution X-ray spectroscopy systems.