An equivalent circuit that emulates the average functional behavior of a saturable reactor (SR) is developed and applied to simulate Magnetic Amplifier (Magamp) post regulators. The equivalent circuit produces a voltage coded signal which is proportional to the effective duty cycle (Do N) of the regulator. The proposed approach converts the switching circuitry of the Magamp post regulator to a SPICE compatible equivalent circuit by replacing the SR and the switched inductor with their respective equivalent-circuit models. The resulting equivalent circuit of the system can then be used to simulate the large and small signal behavior of the regulator under static and dynamic conditions. The proposed approach was verified by comparing simulation results to previously reported analytical and experimental data. The two sets of independent results were found to be in excellent agreement. The paper demonstrates how the proposed model can be used to simplify the analysis and design of practical Magamp post regulators.