Integrated FET and charge reset device for gamma spectrometers

A specially designed and processed five-terminal device incorporating a low-noise field-effect transistor and an integrated charge-restoration mechanism has been used with an HPGe (high-purity germanium) coaxial detector to produce a high-rate, high-resolution gamma spectrometer. A controlled charge pulse is injected into the FET channel and then collected by the gate to discharge the feedback capacitor and reset the amplifier. The reset time is fast, and the high resolution is maintained at energy rate products in excess of 10/sup 11/ eV/s. The FET input capacitance is 8 pF, and the noise voltage is 0.45 nV/ square root Hz at optimum temperature. When it is used with a 22-pF HPGe n-type coaxial detector, the total pulser noise is 420 eV at 12- mu s amplifier peaking time.<
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