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Current-Mode Multifunction Filters and Quadrature Oscillator Using Unit Gain Cells
Jiun-Wei Horng, Chun-Li Hou, Chun-Ming Chang, Wen Yaw Chung and Han Wei Tang

A circuit configuration for realizing current-mode highpass, bandpass and lowpass filters, simultaneously, using two unity-gain current followers, two unity-gain voltage followers, four resistors and two grounded capacitors is presented. The proposed multifunction filters offer the following features: by connecting appropriate output current nodes, the notch, allpass and another highpass filters can be obtained; no requirements for components matching conditions except for the allpass response; orthogonally controllable of resonance angular frequency and quality factor; low active and passive sensitivities and employing only grounded capacitors. From the proposed circuit configuration of current mode multifunction filters, by feedback the output voltage signal via a resistor as voltage to current converter. A new quadrature oscillator circuit can be obtained. The proposed quadrature oscillator offers the following features: both voltage-mode and current-mode quadrature signals can be simultaneously obtained from the same circuit configuration; the oscillation condition and oscillation frequency are independently controllable through different resistors; low active and passive sensitivities and employs only grounded capacitors.

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