Design of a 12.8-Gb/s InP HBT limiting amplifier with cross-point control for driving a distributed modulator driver

Abstract

A 12.8-Gb/s InP HBT limiting amplifier for driving a distributed modulator driver has been designed. The limiting amplifier has cross-point and gain-control features. The key block of the amplifier is a cascode emitter-coupled pair with Schottky diode output clamps to achieve the limiting function. The cross-point feature is realized by generating a DC offset current for the emitter-coupled pair. The limiting amplifier was fabricated in a 1.5-/spl mu/m InP HBT process. The measured cross-point control range and rise/fall time are 33% to 83%, 15.8ps/10.4ps respectively.