Realization of lowpass and bandpass leapfrog filters using OAs and OTAs

The systematic procedure for realizing lowpass and bandpass leapfrog ladder filters using only active elements is presented. The proposed architecture is composed of only two fundamental active building blocks, i.e., an operational amplifier (OA) and an operational transconductance amplifier (OTA), without external passive element requirement, making the approach conveniently for further integrated circuit implementation with systematic design and dense layout. As illustrations to demonstrate the systematic realization of current-mode ladder filters, a 3rd-order Butterworth low-pass filter and a 6th-order Chebyshev bandpass filter are designed and simulated using PSPICE.