Integrated Circuit Charge Sensitive Preamplifier

An integrated circuit charge-sensitive preamplifier has been designed for use with gas filled proportional counters and/or silicon nuclear particle detectors. The circuit uses positive current feedback to achieve open loop voltage gains over 2000. The preamplifier noise with zero input capacitance is 1750 ion pairs (rms) which is equivalent to 14.3 kev (FWHM, silicon detector). The rms noise versus capacitance is 50 ion-pairs per picofarad. Charge sensitivity was found to be essentially independent of external input capacitance. The low frequency open loop gain can be increased by the addition of an external capacitance across the feedback resistor. This also has the effect of increasing the amplifier bandwidth.