A Stable Digital Impedance Circuit Design Method for Resistive Source Impedances

The recent discovery that the input impedance of digital impedance circuits is dependent on the external source impedance requires the development of new design procedures to address the significant complexity of this discovery. These circuits are of particular utility for the implementation of difficult non-Foster impedances such as negative capacitance. Therefore, a new digital impedance circuit design procedure is presented where stable digital filter coefficients are computed to provide desired digital impedance values at two chosen frequencies, given that a stable solution exists. The new design procedure explicitly addresses the aforementioned dependence on the external source impedance for digital impedance circuits with resistive sources. Lastly, simulation results from a negative capacitance design example are compared to the new theory to confirm the efficacy of the new design procedure.