Design of electronically tunable ladder filters using current-controlled current differential buffered amplifiers

A realization of electronically tunable ladder filters using current-controlled current differential buffered amplifiers (CCDBAs) is proposed. First, this paper introduces the bipolar implementation of CCDBA. Second, the design procedure for the systematic realization of general current-mode ladder filters is also proposed. The proposed method is based on simulating RLC ladder prototypes using only proposed CCDBAs and grounded capacitors without the employment of external passive resistors. The characteristics of the obtained filters can electronically be controlled by the bias current of CCDBAs. To demonstrate the proposed approach, a 5^th-order Butterworth lowpass and a 6^th-order Chebyshev bandpass filters are realized as design examples. Finally, simulation results that support the theoretical analysis are included.