High-input impedance first order all-pass filters using DDCC

This paper presents three voltage-mode first order all pass filters using differential difference current conveyors (DDCC) as the active elements. The first circuit has one DDCC, one capacitor and one grounded resistor. The second circuit also employs one DDCC, one resistor and one grounded capacitor. The third circuit uses two DDCC, one resistor and one capacitor and both the elements are grounded. These circuits have the following advantages: high input impedance, low passive sensitivities and no requirements for component matching conditions and in the third circuit all passive components are grounded and thus it is preferred for integrated circuit implementation. Theoretical results are verified using PSPICE simulation.