LOW-NOISE CMOS PREAMPLIFIER-SHAPER FOR SILICON DRIFT DETECTORS

We have designed a 16-channel preamplifier-shaper for particle trackin g using silicon drift detectors (SDD). The preamplifier, which is opti mized 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 l inearity (< 0.5% to 50 fC), and good tolerance to process variations a nd temperature and power supply fluctuations. The circuit is continuou sly sensitive, has no digital signals on chip, and requires no externa l components or critical adjustments. The peaking time of the shaper i s 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 acc omodate detector leakage currents of up to 1.5 uA. Although the circui t was developed for use with particle tracking detectors, these techni ques are also well-suited for the design of lower-noise preamplifiers for high-resolution X-ray spectroscopy systems.