Electronically Controlled Biquadratic Filter and Quadrature Oscillator Using CDTAs

This article presents a current-mode biquadratic filter and quadrature oscillator circuit based on current differencing transconductance amplifiers (CDTAs). The proposed circuit does not require changing the circuit topology. In addition to the low-pass filter, high- pass filter, band-pass filter, and sinusoidal quadrature signal, the proposed circuit has a pole frequency that can be controlled independently from the quality factor, while the oscillation frequency can be controlled non-interactively. The circuit impedance with high output can directly drive the load without using a current buffer. Furthermore, grounded capacitors can function without the use of external resistors. This qualification is ideal for the future development of integrated circuits (ICs). After the PSPICE simulation with 90 nm CMOS parameters and the experiments by commercial ICs, the results are consistent with the theoretical analysis of the proposed circuit.