New general immittance converter JFET voltage-controlled impedances and their applications to controlled biquads synthesis

Two new general immittance converter (GIC) JFET configurations for the realization of voltage-controlled impedances (VCI's) are proposed. Compared with previously reported structures, the circuits exhibit wide dynamic range and low distortion properties that are frequency independent, even for nonresistive VCI's. We consider the influence of op-amp frequency dependent gain and derive conditions for obtaining high Q-factor inductances and capacitances. We also present computed and experimental results for several voltage-controlled GIC-type biquads that are built based on the proposed circuits.