A one port device realized using a GIC (general impedance converter) whose impedance Z_in is given by 1/(s²D), where s = jω and D is a constant. A circuit realization is shown in the diagram, where D = C²R₂R₄/R₅. If, for example, C = 1 farad and R₂ = R₅ = 1 ohm and R₄ = R, then Z_in becomes equal to −1/(ω²R), i.e. a frequency-dependent negative resistor. This device is used extensively to design active filters directly from passive LC prototype filters.

Frequency-dependent negative resistor