GeFRO: a New Charge Sensitive Amplifier Design with a Minimal Number of Front-end Components

TL;DR

The paper introduces GeFRO, a novel charge sensitive amplifier with minimal components, featuring dual outputs for high-resolution and fast timing in semiconductor radiation detector readouts.

Contribution

It presents a new front-end circuit design with a simplified structure and dual outputs, improving timing resolution and noise performance for radiation detection.

Findings

Fast signal bandwidth >20 MHz for timing and pulse discrimination

Achieved timing resolution around 20 ns

Noise level of approximately 160 electrons RMS with 26 pF input capacitance

Abstract

A new approach was developed for the design of front-end circuits for semiconductor radiation detectors. The readout scheme consists of a first stage made of only a few components located close to the detector, and of a remote second stage located far from the detector, several meters away. The second stage amplifies the signals from the first stage and closes the feedback loop to discharge the input node after each event. The circuit has two outputs: one gives a "fast" signal, with a bandwidth larger than 20 MHz, allowing to preserve the high frequency components of the detector signals, which may be useful for timing measurements, pile-up rejection or pulse shape discrimination. The second output gives a "slow" signal, whose gain depends only on the value of the feedback capacitor, as happens with a classic charge sensitive amplifier, allowing to obtain higher resolution and lower drift. The prototype was named GeFRO for Germanium front-end, and was tested with a BEGe detector from Canberra. The wide bandwidth of the "fast" signal gave a timing resolution of the order of 20 ns. The noise of the circuit at the "slow" output after a 10 us Gaussian shaping was close to 160 electrons RMS with an input capacitance of 26 pF.