The 1N6045A transorb is to protect the circuit from surge voltage. The 0.1 and 2.2 micro Farad capacitors are to lower the low frequency phase noise.
The benefits of the active bias are: one, it provides a stable, close-loop power supply. Two, by varying R1 and/or R2, we can vary VCE and IC almost independently. The figure below shows the results from Electronic Workbench® Click for a full size picture.
| Introduction | Measurements | Fundamental Theory | Transistor Selection |
| Terminating Network Design | Load Network Design | Coarse Tune Design |
| DC Bias Circuit Design | Fine Tune Design | Phase Noise |