Source degeneration as series-series feedback

Field effect transistor (FET) or bipolar junction transistor (BJT) based circuits, involving emitter/source degeneration by any general impedance are widely known for their positive effects on circuit performance. The circuit´s behavior like input-output impedances, trans-admittance, voltage and power gains of such topologies are well known. In this paper, we propose to analyze the topology by looking at it as a local series-series feedback. The validity of the approach is demonstrated on RF CMOS 0.18 μm TowerJazz commercial process. This method, based on the negative feedback analysis, gives an instructive insight on the advantages of using source degeneration in analog and microwave circuits.