The nonlinear drain-source capacitance effect on continuous-mode class-B/J power amplifiers

Mokhti, Zulhazmi A., Lees, Jonathan ORCID: https://orcid.org/0000-0002-6217-7552, Cassan, Cedric, Alt, Alexander ORCID: https://orcid.org/0000-0002-7621-4940 and Tasker, Paul J. ORCID: https://orcid.org/0000-0002-6760-7830 2019. The nonlinear drain-source capacitance effect on continuous-mode class-B/J power amplifiers. IEEE Transactions on Microwave Theory and Techniques 67 (7) , pp. 2741-2747. 10.1109/TMTT.2019.2918309

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Abstract

The effects of the nonlinear drain-to-source capacitance (CDS), or the varactor effect, on the operation of continuous-mode class-B/J power amplifiers (PAs) are described in terms of the mathematical analysis as well as experimental validation. The nonlinear CDS generates harmonic current when the class-B/J drain voltage is applied across it, modifying the theoretical load trajectories on the Smith chart. This is shown to significantly deviate from the continuous-mode assertion of constant power and efficiency. A novel measurement approach called voltage-pull is used to investigate the effects of the second harmonic generation by the varactor in a class-B/J PA mode. Theoretical and experimental results showed the nonlinear CDS degrades the drain efficiency compared to class-B on one half of the class-B/J design space while improving the other half due to the energy upconversion and downconversion, respectively. This paper provides an approach for die nonlinear characteristic optimizations for transistor manufacturers.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Engineering
Publisher:	Institute of Electrical and Electronics Engineers (IEEE)
ISSN:	0018-9480
Date of First Compliant Deposit:	24 May 2019
Date of Acceptance:	5 March 2019
Last Modified:	12 Nov 2024 23:45
URI:	https://orca.cardiff.ac.uk/id/eprint/122860

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