Small Signal Amplifier Design
Stephen I. Long · River Publishers eBooks · 2023
The measured S-parameters can be used to accurately design the amplifier. The S-parameter design technique employs relationships between input and output powers, and forward and reflected powers, which look scary at first but can easily be derived using the signal flow graph method and Mason’s gain rules. The traditional methodology using Rollett’s stability factor is based on S-parameters. The direct current blocking capacitors at the input and output have been designed to be series-resonant at the operating frequency. The S-Parameter model should be replaced with a nonlinear device model and bias insertion circuitry added. The device can be biased to the desired value and stability evaluated once again. The bias network potentially can add an undesired feedback loop. The circuit is known to be stable when ideally terminated. The internal resistances could mask negative resistances that would lead to instability.