Preamplifiers

INTRODUCTION

The preamplifier associated with radiation detectors performs three essential functions:

• Conversion of charge to voltage pulse
• Signal amplification
• Pulse shaping

Most preamplifiers in use today are charge sensitive, and provide an output pulse with an amplitude proportional to the integrated charge output from the detector. General purpose preamplifiers have a RC feedback network which results in a quasi-step function output. For extremely low noise detectors (Si(Li) and Low Energy HPGe), the feedback resistor is eliminated and the output signal becomes a true step function, which builds up in random staircase fashion, and is reset by feedback circuitry. For many high count rate and high resolution applications with HPGe detectors, the Transistor Reset Preamplifier (TRP) offers the best performance.

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