Optimized multi-stage amplifier compensation method for wide load variations
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Due to variations in process, voltage, and temperature (PVT), amplifiers are almost solely designed for use in a negative feedback loop. The feedback loop mitigates the effect of PVT, however maintaining stability becomes the main design challenge. Further, multi-stage amplifiers with high open-loop gain are used for powering headphone speakers in modern portable electronics. As there are many different headphone manufacturers and compatibility specifications, headphone amplifiers are subjected to a wide variation in capacitive and resistive loads, which further complicates the stability upkeep. This thesis explores a two-stage (Common-Gate Feedback) and three-stage (Impedance Adapting Compensation) amplifier topology with respect to performance under wide load variations. For both compensation topologies, an analytical analysis is presented, followed by a design proposal for a headphone amplifier application. Finally, the trade-offs for maintaining stability under varying loads are discussed.