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A new high input impedance filter employing three current feedback amplifiers (CFAs) and six passive elements, three of them are grounded, is presented. The proposed circuit offers the following advantages: simultaneous realization of lowpass (LP), bandpass (BP) and highpass (HP) filtering functions, employs two grounded capacitors, exhibits high input and low output impedances which permits easy cascade connection, low passive sensitivity figures and orthogonal control of resonance frequency (ω_o) and bandwidth (ω_o/Q). PSPICE simulation results are given to verify the theoretical calculations.

A new linear voltage-controlled oscillator (LVCO) implementation using single AD-844 CFA with a pair of AD-835 multiplier devices and a pair of grounded capacitors is proposed. The open-loop transfer function of the topology is analyzed wherein the concept of Short-Circuit Natural Frequency (SCNF) is applied to derive the sinusoid oscillator implementation. The proposed oscillator circuit is then restructured to yield a linear voltage-controlled quadrature oscillator (LVCQO) after appropriate cascade with a CFA-based active integrator. The oscillation frequency is linearly tunable ($f_o\sim 13.2$MHz) by the multiplier control voltage ($V)$. Subsequently, a high-$Q$ selective band-pass (BP) filter is derived. Effects of the CFA port roll-off parameters and its parasitic capacitors ($C_{y,z})$ had been analyzed to be negligible. Measured oscillator response exhibited a THD $\sim 1.8$%, a linearity error ($\mathrm{\Delta })\sim 2.4$% and a phase noise figure of ($-)$104 dBc/Hz at 24-kHz offset.