Stability Analysis of Non-Foster Impedance Inverters

Recently, active impedance inverters based on non-Foster negative capacitors have been proposed for applications in widely tunable filters. These designs use a traditional Linvill’s topology of the negative capacitor. Unfortunately, the range of external loads needed for the stable operation of such active inverters is rather limited. However, there is also the negative capacitor based on a recently proposed loss-compensated passive structure. This novel design promises stability-robust behavior for an extremely wide range of external loads. In this study, we compare the stability properties of both approaches and show that the design based on the loss-compensated passive structure is more robust.