1 Answers
A frequency dependent negative resistor is a circuit element that exhibits a purely real negative resistance -1/ that decreases in magnitude at a rate of -40 dB per decade. The element is used in implementation of low-pass active filters modeled from ladder filters. The element is usually implemented from a generalized impedance converter or gyrator. The impedance of a FDNR is
Z = 1 s 2 k C {\displaystyle Z={\frac {1}{s^{2}\mathrm {kC} }}} or
Z = − 1 ω 2 k C {\displaystyle Z={\frac {-1}{\omega ^{2}\mathrm {kC} }}} when s = jω.
The definition and application of frequency dependent negative resistors is discussed in Temes & LaPatra, Chen and Wait, Huelsman & Korn. The technique is attributed to L. T. Bruton.