The presence of fluctuations in the power and ground supply rails affect the quality of various performance metrics (gain, phase, impedance, transient response, etc.) of any analog and mixed-signal system. In this paper, a generalised indefinite admittance matrix (GIAM) method is proposed to formulate these metrics for active circuits. The proposed analysis includes the impact of deterministic supply noise on performance parameters. For the purpose of analysis, a common source amplifier, designed in a standard CMOS 180 nm technology, is analysed. The maximum mean percentage error between analytical results and Cadence® Virtuoso® tool simulations for the amplifier is less than 4 % for all the cases. © 2020 IEEE.