UC Irvine

A Broadband Transimpedance Amplifier for Optical Receivers

By

Alireza Karimi Bidhendi

Master of Science in Electrical Engineering and Computer Science

University of California, Irvine, 2018

Professor Payam Heydari, Chair

This work presents a broadband transimpedance amplifier (TIA) for optical communication serial link front-ends, achieving 50 GHz of bandwidth. A brief background on the applications of TIAs, their design specifications and performance enhancement techniques are presented. Next, a TIA is introduced which is comprised of three stages and uses several techniques to enhance the bandwidth while maintaining a flat frequency response and limit the frequency peaking. The first stage is a shunt-peaked, shunt-series feedback stage incorporating a transformer-based positive feedback. The second and third stages are RC-degenerated common-emitter stage and an inductively degenerated emitter follower. An integrated 100 fF metal-insulator-metal capacitor shunts the TIA input to emulate the photo-diode junction capacitor. Analytical analysis and circuit and electromagnetic simulations is performed and compared with the measured results. Design is implemented in TowerJazz 0.13µm SiGe BiCMOS process occupying 0.58 mm2 (including pads) of die area and dissipates 24 mW from a 2 V supply voltage (resulting in an energy efficiency metric of less than 0.5 pJ/bit). Transimpedance gain of 41 dBΩ and an input-referred current-noise spectral density of 39.8 pA/√Hz over the bandwidth are measured. The TIA achieves an open eye diagram at 50 Gb/s with a random rms jitter of 2.3 ps, including the jitter contribution of the test fixture and input source.