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Title: Design and development of low distortion bipolar voltage-to-current converters for RF applications
Author: Mathew, Mary
ISNI:       0000 0001 3621 165X
Awarding Body: Oxford Brookes University
Current Institution: Oxford Brookes University
Date of Award: 2007
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The research work described in this thesis is concerned with the analysis and design of low distortion voltage-to-current (V-I) converter bipolar junction transistor circuits. In this thesis, various voltage-to-current converter circuits published in the past have been reviewed by the author in order to understand the different techniques employed to improve the linear operating range, total harmonic distortion and transconductance. Throughout this research, the emphasis has been to improve the above mentioned parameters. All the V-I converter circuits reported have been simulated using PSpice and the results compared with the values obtained by theoretical analysis. The majority of the results of this work have been reported by the author; see Chapter 10 at the end of this thesis where all 5 publications by the author can be found in full. It was necessary to obtain precise values for certain parameters, in particular, transition frequency (fT), Early voltage (VA) and current gain (P) of the transistor to facilitate the design process. This was done using an extensive set of simulations for the transistor operating at different collector current levels. A commonly encountered requirement of the V-I circuits is an accurate non-integer ratio of current biasing. Several published such biasing schemes were studied and three new designs were conceived and evaluated. In the next part of the work several V-I converter circuits were reviewed to understand the various existing techniques and their limitations. These can be conveniently classified into three main classes of technique, namely (i) boosted-gm (ii) cross-coupled, and (iii) multi-tanh. Of these, the boosted-gm technique showed the most promise for further exploitation and development. New circuits were then developed using the boosted-gm technique with different types of feedback, classified as collector-base feedback, collector-emitter feedback and global feedback. In terms of the preferred circuit performance, these were assessed by an arbitrary but convenient, figure-of-merit (FOM) which is defined as (THDRxBW)/PD where THDR, in dB is the total harmonic distortion .reduction, BW is the 3dB bandwidth and PD is the power dissipation. On this basis, the best value of FOM (2421.24 dBMHz/mW) was achieved with the circuit called Type 2B in this thesis, which is based on collector-emitter feedback.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available