New measurement results and models for non-linear differential amplifier characterization

Previously, the author described a system that provides true differential and common-mode stimulus for CW and modulated RF signals, and presented results of non-linear operation of devices driven with such signals, which were compared with the same devices driven at the same levels using single-ended drive and calculating the differential response. Those devices showed no difference in the differential gain terms whether measured with truemode or single ended measurements. In this paper, new results on limiting amplifiers demonstrate substantial change in the differential gain compression when measured using true differential mode drive. A theoretical model is developed which considers circuit topology differences and predicts wbich devices will have non-linear characteristics that change depending upon the test methods.