The Electronics Instrumentation Service of the Insittute of Cosmos Science of the University of Barcelona (ICCUB-SiUB) is focused on developing ultrafast readout electronics for high-energy physics and medical imaging. In the framework of the HERD project (High Energy Cosmic-Radiation Detector) the group has developed the readout BETA-ASIC to push the limits of dark matter radiation research. Thus, the aim of this Master Thesis is to contribute to the ASIC design. This project presents a low power comparator that will be used for detection triggering as well as internal path selecting of a multi gain system. The comparator has input rail-to-rail and hysteresis feedback. The power consumption is around 60\ \mu W, the gain is 76\ dB and the hysteresis amplitude is about 5.75\ mV. The single-photon SNR is around 10, the delay is 15\ ns and jitter is below\ 100\ ps for input energies higher than 10 pe (photoelectrons). These simulations prove the fulfilment the requirements for the ASIC, and a first prototype has already been sent to be manufactured in April
