This work discusses the design of analog front-end circuits for future, high-rate pixel detector applications. In particular, the paper describes the in-pixel flash ADC, featuring a novel, clocked comparator conceived to dramatically reduce the threshold dispersion of the front-end. The paper includes a description of the front-end channel blocks, together with the discussion of the main analog performance parameters, as obtained from circuit simulations and including equivalent noise charge and threshold dispersion. The design is carried out in the framework of the INFN Falaphel project.