Solid State Circuits Society

October 16, 2003

Our speaker was Mr. George Vendelin , and the topic of his presentation was
“Lossless Feedback Amplifier Design”

As more customer demand, activity and resources become available for designing RF circuits as part of a system on a chip it will become necessary to include some microwave theory in the ASIC designers knowledge base. We are indeed fortunate to have George Vendelin available this evening to share his knowledge with us on some of the intricacies of microwave amplifier design.

His talk addresses the topic of lossless feedback networks for three types of amplifiers:
1) High Gain – Mason’s Unilateral Gain Amplifier achieved by designing a lossless feedback network to cancel (unilateralize) S12, the reverse gain of the amplifier, thus not having to compromise gain for stability. Several feedback topologies are examined.
2) LNA – Vendelin 1975 Low noise design using emitter/source inductors to achieve Fmin and S11′ = 0. This examines how to optimize the input match of an amplifier while simultaneously obtaining low noise figure.
3) HPA – The dual of (2) where max P1dBC is achieved with S22′ = 0. This examines a high power amplifier optimized for output match, S22′ at the 1 dB compression point.
Some of this talk was published in IEEE Microwave Wireless Components Letters, March 2003, p 110.
George Vendelin will become an IEEE Life Fellow in October,2003. He currently teaches at Stanford, Santa Clara University, San Jose State University, and University of California Berkeley Extension since 1976. His research interests includes nonlinear models of microwave devices and circuits and is one of the authors of ‘Microwave Circuit Design – Using Linear and Nonlinear Techniques’; 2nd edition late 2003. He also wrote ‘Design of Amplifiers and Oscillators by the S-Parameter Method’; 1982, John Wiley. He is a consultant for microwave circuit designs.

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