Current-mode high-Q bandpass filter and mixed-mode quadrature oscillator using ZC-CFTAs and grounded capacitors

This paper presents the realization of the current-mode bandpass filter and mixed-mode quadrature oscillator both from the same circuit configuration. The proposed circuit is in the resistor-less structure, which contains only four z-copy current follower transconductance amplifiers (ZC-CFTAs) as active components together with two grounded capacitors as passive components. As the first configuration, the current-mode BP filter with high quality factor (Q) is proposed. The center frequency (wo) and the Q of the circuit are orthogonal adjustable via the gm-value of the ZC-CFTA. From the same topology, the mixed-mode quadrature oscillator can easily be realized that is capable of generating two explicit quadrature current outputs and two quadrature voltage outputs, simultaneously. Moreover, the realized oscillator also provides the advantage of orthogonal electronic control of the oscillation condition and oscillation frequency, which makes it suitable as variable frequency oscillator. PSPICE simulation results using bipolar ZC-CFTA have been given to verify the workability of the two proposed circuits.