Design of a charge sensitive preamplifier on high resistivity silicon

A low-noise, fast, charge-sensitive preamplifier was designed on high-resistivity, detector-grade silicon. It is built at the surface of a fully depleted region of n-type silicon, allowing it to be placed very close to a detector anode. The preamplifier uses the classical input-cascode configuration with a capacitor and a high-value resistor in the feedback loop. The output stage of the preamplifier can drive a load up to 20 pF. The power dissipation of the preamplifier is 13 mW. The amplifying elements are single-sided gate JFETs developed for this application. Preamplifiers connected to a low-capacitance anode of a drift-type detector should achieve a rise time of 20 ns and have an equivalent noise charge, after suitable shaping, of less than 50 electrons. This performance translates to a position resolution better than 3 mu m for silicon drift detectors.<>