A Low Noise High Gain Bandwidth Charge Sensitive Preamplifier

The concept of the charge sensitive amplifier is discussed and a novel method for obtaining a high gain amplifier stage through the use of a positive current feedback dynamic plate load is described. It is shown that under certain conditions this type of feedback can provide increased bandwidth as well as increased low frequency gain. The schematic of a preamplifier embodying these principles is given and its performance is described. The measured noise, with no external capacitance, is 510 r.m.s. electrons for equal integration and differentiation time constants of 1 μsec. The measured risetimes for closed loop gains of 100 and 1000 are 25 and 96 nanoseconds respectively. Linearity and gain sensitivity data are also included.