A graphic design method for matched low-noise amplifiers

A graphic design method for matched low-noise amplifiers is presented in which all necessary design information is given in the load plane. It is possible to work exclusively in the load plane, as the input-matching requirement makes the source admittance dependent on the load admittance. As a consequence of the bilinear transformation involved, all parameters may be presented by circles. Analytic equations giving the centers and the radii of the circles in the load plane are presented. Two kinds of amplifier configurations are considered: a single-stage amplifier with an input-match requirement and a two-stage cascade amplifier. The latter is required to have an output match and noise-optimized second stage, in addition to an input match. For the single-stage case the noise figure, the power gain, the stability, and the input network are treated. In the cascade design, the total noise figure, the interstage network, and the available gain are treated as well. A design example for the case of lossless feedback is presented.<
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