Broadband filter design

Abstract

This thesis presents the design of an active filter implemented in a 65nm CMOS technology and based on super source follower. The original filter was 5th order low-pass Chebyshev-type with a cut-off frequency of 160 MHz, but it was to be changed into Butterworth-type because of the results, here both designs are shown. The architecture is fully differential and it is based on Sallen-Key biquad structures with super source follower as an active element and resistors and capacitors as passive elements. The design process starts with a study of the super source follower and a comparison of this circuit with the normal source follower. After that the work is divided into different stages in order to get an easy design flow, starting with ideal models including limited bandwidth and gain, and then simulations with transistor level active elements are performed. Finally, some measurements are presented to analyze the noise and linearity performance of the filter.