The design of GaAs HEMT and HBT Bessel-type transimpedance amplifiers

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Title: The design of GaAs HEMT and HBT Bessel-type transimpedance amplifiers
Author: Adeyemi, Oluwafemi Ibukunoluwa
Abstract: The need of the everyday user to transfer large amounts of data is driving the need for larger data transfer capacity . Optical communication networks can satisfy this need . To be economically viable , optical transceivers must be integrated onto chips at low cost , using relatively cheap semiconductor processes . The optical preamplifier (transimpedance amplifier ) receives optical information and converts it to a useful electrical form . It must operate at high speed , contribute little distortion to the input signal , and add little electrical noise to the incoming signal . This thesis investigates the design techniques in the literature , and proposes new architectures . Two high performance preamplifiers are designed , one using GaAs HEMTs , and the other using GaAs HBTs , each with different circuit techniques . The HEMT preamplifier has a transimpedance gain of 1 .4 k ? ? ? ? ? ? , the highest in the literature for 10 Gb /s operation , along with a low input referred noise current of about 15 pA /Hz1 /2 at a bandwidth of 6 .3 GHz . The HBT preamplifier also has a transimpedance gain of 1 .5 k ? ? ? ? ? ? , with a low input referred noise current of about 7 pA /Hz1 /2 . Both have clear , open eye -diagrams with a 10 Gb /s bit stream input , and are suitable for integration on a chip . The HEMT preamplifier was implemented as a common -gate , common -source amplifier cascade with a darlington output driver for a 50 ? ? ? ? ? ? load . The HBT preamplifier was implemented as common -emitter darlington amplifier with shunt peaking , and a simple emitter degenerated output driver for a 50 ? ? ? ? ? ? load . Both implementations exceeded the bandwidth , transimpedance gain and noise performance typically expected of the transistor technologies used . It is shown that the transimpedance limit can be circumvented by the use of novel architectures and shunt peaking .
URI: http : / /hdl .handle .net /1969 .1 /4663
Date: 2007-04-25

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The design of GaAs HEMT and HBT Bessel-type transimpedance amplifiers. Available electronically from http : / /hdl .handle .net /1969 .1 /4663 .

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