Design of the analog front-end for the Timepix3 and Smallpix hybrid pixel detectors in 130 nm CMOS technology

Abstract

This paper describes a front-end for hybrid pixel readout chips, which was developed for the Timepix3 and Smallpix ASICs. The front-end contains a single-ended preamplifier with a structure for leakage current compensation which can handle both signal polarities, and a single-threshold discriminator with compensation for pixel-to-pixel mismatch. Preamplifier and discriminator are required to be fast, to allow a Time-Of-Arrival (TOA) measurement with a resolution of 1.56 ns. Time-Over-Threshold (TOT) is also measured, the monotonicity of TOT with respect to the input charge is greatly improved as compared to the previous Timepix chip. The analog area is only 55 μm × 13.5 μm. Timepix3 has already been fabricated and the first test results are also presented in this paper.