The canonical circuit introduced is an activeRCcircuit using a single operational amplifier, and its input admittance is composed of a frequency-dependent negative resistance (f.d.n.r.) in parallel with a resistor and a capacitor. The quality factor of the proposed circuit can be independently controlled by means of a single grounded resistor. Passive sensitivities and the effects of the nonideal op-amps are given. Applications of the parallel resonator in lowpass and bandpass filters are discussed. Finally, experimental results are presented