RF Electronics Chapter 8: Amplifiers: Stability, Noise and Gain Page 277
2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0.
Requirement for Stability
For power amplifier design, a single power transistor, or several combined in parallel, are
used to provide the required amplification at the required frequency, with the required
linearity. The amplifier should be stable and not oscillate at any frequency under normal
operating conditions. Amplifier stability and matching of input and output, ensuring that
the highest power output is obtained, are the most critical parameters in a power amplifier
design.
Smith Chart Revision
Figure 8.3. Smith Chart; a plot of the normalised reflection coefficient, .
To ensure that the amplifier is matched at the input and output, normally the return loss
S
11
at the input and S
22
at the output of the amplifier is measured. In order to be able to
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