Realization of Lowpass and Bandpass Leapfrog Filters Using OAs and CCCIIs

Abstract

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 a Current Controlled Conveyor II (CCCII), without external passive element requirement, making the approach conveniently for further integrated circuit implementation with systematic design and dense layout. The characteristic of the current transfer function can be adjusted by varying the external bias currents of CCCIIs. 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.

Operational Simulation of LC Ladder Filter Using VDTA

“…The drawback of this configuration is that a floating capacitor is generally required and this degrades the performance of the derived filter topology in high frequency application. In the third approach, operational simulation or leap-frog method [23][24][25][26][27][28][29][30], simulation is carried out for the operation of ladder rather than its component.…”

“…Literature survey reveals the operational simulation of ladder filter using operational amplifier (OA) and current controlled conveyor (CCCII) [24], OTA [25,26], CC [27], multiple output second generation current controlled conveyor (MO-CCCII) [28], current feedback amplifier (CFA) [29], and CFOA [30]. This paper presents a systematic approach for operational simulation of LC ladder filter using voltage differencing transconductance amplifier (VDTA).…”

“…(i) Lesser numbers of active blocks are used as compared to [24,26,[28][29][30]. (ii) There is no use of resistors in realization, while [25,29,30] use both floating and grounded resistors and [27] uses only grounded resistors.…”

Electronically Tunable Current-mode High-order Ladder Low-pass Filters Based on CMOS Technology

“…These realizations require many active building blocks and use floating resistors and may, therefore, be not suitable for integration. A different realization method of low-pass leapfrog filters was presented in [15]. The proposed realization uses the second-generation current-conveyor (CCII) and exploits to advantage the frequency-dependence of the differential gain of the operational amplifier (OA) for implementing an integrator.…”

“…The proposed realization uses the second-generation current-conveyor (CCII) and exploits to advantage the frequency-dependence of the differential gain of the operational amplifier (OA) for implementing an integrator. While avoiding the use of externally connected passive components is an advantage, the proposed circuit in [15] lacks electronic tuning of the filter parameters and requires a relatively large number of active devices. In [16] the multiple outputs current conveyor (MOCC) was used to synthesize the low-pass filter (LPF) from the LC ladder prototype.…”