CMOS programmable gain circuits: Amplifiers and current conveyors.

摘要

CMOS programmable gain stages form essential building blocks in today's telecommunication systems. For each specific application, there may be a myriad of potential solutions; however, not all solutions are equally suited to solving all problems. Some problems may be directly treated with traditional voltage-mode approaches while other problems may be more efficiently tackled via less conventional current-mode methods. In view of such an expansive landscape, the present work seeks to investigate two telecommunication applications and the specific solution for each.; Firstly, a traditional Programmable Gain Amplifier (PGA) is designed for use in Very High-Speed Digital Subscriber Loops (VDSL). Wide bandwidth, low noise, and high linearity are achieved using a fully differential, multi-stage, voltage-mode amplifier with switched resistive feedback to set the gain. The pseudo-constant signal bandwidth is accomplished using switched nested Miller compensation for each gain setting to keep the closed-loop bandwidth relatively constant.; Secondly, a novel Programmable Gain Current Conveyor (CCII) is designed for use in a T1/E1 Equalizer Line Interface Unit (LIU). Being digitally tunable, the open-loop CCII has high input impedance, low output impedance and constant bandwidth across all gain settings.; Both programmable gain stages have been designed and fabricated in the TSMC CMOS 0.35 mum process. Detailed analysis, simulation and measurements are shown within this thesis.