An ultra-fast low-noise preamplifier for Low Gain Avalanche Detectors

The Low Gain Avalanche Detector (LGAD) is a novel Silicon detector with precise timing and fast response. To study the transient response of LGADs, we need to obtain the detector signal using Transient Current Technique (TCT), for which a preamplifier with high bandwidth and low noise is required. Currently, the most widely used preamplifier board in the LGAD community is developed by University of California, Santa Cruz (UCSC). In this paper, we will introduce a newly designed LGAD preamplifier board. Compared with the UCSC board, the performance has been fully improved. The board contains a transimpedance amplifier and two-stage voltage amplifiers. The total charge gain of our preamplifier reaches 20.58 mV ns/fC, with good linearity in the input dynamic range of [0.7 fC, 66 fC]. The −3-dB bandwidth is about 870 MHz, meeting the demands of LGAD amplification. We conducted 90Sr β-scope tests using our preamplifiers and HPK 3.1 single sensors. The equivalent noise charge at 20 °C is 0.27 fC. The jitter contributed by our preamplifier is about 7.12 ps. The results show that our single-channel preamplifier has lower noise and better time resolution than the UCSC boards. Besides, a 9-channel preamplifier board is developed for multi-pad LGAD readout. All channels have good uniformity and low noise. Our preamplifier boards can be well applied in β-scope or laser-scanning TCT tests of LGADs.