Negative impedance converters (NICs) are used to create impedance loads that can effectively cancel the inductive properties of magnetic dipoles, resulting in active metamaterials with increased bandwidth and reduced loss for µ-near-zero (MNZ) and negative-Re(µ) (MNG) media. We demonstrate techniques for analyzing the stability and characterizing the magnetic properties of effective media loaded with NICs. Specifically, we apply the Nyquist criterion to validate the stability of sample active metamaterials. It is shown that the practical NIC-loaded metamaterial may maintain stability and reduce dispersion, albeit with reduced performance as compared to the ideal NIC load.