Development of a low-impedance traveling wave amplifier based on InAlAs/InGaAs/InP-HFET for 20 Gb/s optoelectronic receivers

Abstract

The applicability of the transimpedance amplifier for optoelectronic receivers becomes doubtful for bit rates higher than 20 Gb/s. So recently the traveling wave amplifier (TWA) concept for high bit rate receiver systems is of increasing interest because it is the preferred amplifier concept for broadband applications like hierarchically organized communication interlinks. TWAs usually are designed with an input and output impedance of 50 /spl Omega/. Thus a main problem of the TWA-concept for an optoelectronic receiver is matching the photo-detector (PD) and the TWA input and reach the requested input RC-bandwidth. The conventional approach is a TWA with an additional 50 /spl Omega/ match resistor at the input line, which has to be integrated directly into the PD itself in order to avoid parasitics. The aim of this paper is to present an alternative concept to the match resistor realized by a TWA with a low-impedance input (25 /spl Omega/), which yields significantly reduced design and fabrication efforts. All simulations for the investigated and optimized designs of the TWA in coplanar technique have been carried out using a commercially available software. For exact noise and sensitivity simulations, an extended temperature noise model (TNM) for heterostructure field-effect transistors was developed and implemented. Finally a comparison with measurement results of the realized TWA is presented.