RF-SQUIDs are usually modeled as the second order nonlinear electronic systems. The numerical solution to the nonlinear differential equations describing the systems containing the RF-SQUIDs is frequently needed to get the dynamic performances

noise characterizations and optimum operation conditions of the systems

which often proves to be very complicated and timeconsuming because it is involved with such problems as the efficiency

accuracy and reliability of the numerical algorithm chosen

as well as the software programming of the algorithm and its debugging[1] PSpice is employed to do these with great ease because the RF-SQUID equivalent circuit which can be accepted by the PSpice simulator is developted from the nonlinear differential equations describing the RF-SQUIDs.