In this paper, a general structure using dual-output operational transconductance amplifiers (OTAs) is explored to derive new first-order and second-order multi-function filters using OTAs with multiple current outputs and with and without grounded capacitors. Two first-order all-pass filters that have been obtained are presented, together with an analysis of nonidealities of OTAs, viz., finite bandwidth and parasitic output and input resistance and capacitance. Second-order multi-function filters obtained by using OTA-C simulated inductances in the proposed general structure are also presented. The realization of quadrature oscillator using the proposed first-order all-pass networks is also considered. Detailed analysis of nonideal frequency performance of the OTAs as well as finite output and input impedances is presented. SPICE simulation results are also given for the proposed circuits.

Novel First-Order and Second-Order Current-Mode Filters Using Multiple-Output Operational Transconductance Amplifiers

A new electronically tunable universal current mode biquad filter structure employing three multiple output current controlled conveyors (MOCCCII) and two grounded capacitors is presented. The proposed filter offers the following advantageous features: low input impedance and high output impedance--a desirable property of current mode filters; realization of low pass, band pass, high pass, notch, and all pass; no matching constraint; low sensitivity performance and use of grounded capacitors suitable for integration. The practical design problems due to nonlinearities of MOCCCIIs have also been addressed. The feasibility of the design is confirmed via SPICE simulations.

A new electronically tunable current mode universal filter using MO-CCCII

This paper deals with RC active biquad working in the so-called current mode (CM). The design approach uses only three transconductors (OTA) with the minimum necessary number of outputs and with only three passive grounded elements. The proposed filter has simple circuit configuration providing all standard transfer functions such as high-pass (HP), band-pass (BP), low-pass (LP), band-reject (BR) and all-pass (AP). Electronic tuning and independent adjusting of the quality factor and bandwidth of BP filter is possible. The presented circuits are verified by PSpice simulations utilizing OTAs on transistor level of abstraction. The linear parasitic effects of the real active elements in each suggested circuit are briefly discussed. Experimental verification is also given. Designed networks can be used in many applications such as antialiasing filters, in high-speed data telecommunication systems, for signal processing in the cable modems, in regulation and measurement techniques etc.

Current-Controlled Current-Mode Universal Biquad Employing Multi-Output Transconductors

Nodal admittance matrix (NAM) expansion method for systematic synthesis of seven-OTA Wien oscillators is given. The paper presents 32 Wien oscillators using OTAs by means of NAM expansion method. Each oscillator employs seven OTAs and two grounded capacitors, it is easy to be integrated and the oscillation condition and frequency can be tuned electronically, linearly and independently through tuning bias currents of OTAs. The circuit analysis and computer simulation results are in agreement with theory and then the realizability of the derived circuits is verified.

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Systematic synthesis of OTA-based Wien oscillators

A NAM expansion method for systematic synthesis of OTA-based Wien oscillators is given. Moreover, the NAM expansion method for four different classes of the oscillators is considered. The class I oscillators employ three OTAs, the class II oscillators employ four OTAs, the class III oscillators employ five OTAs, and the class IV oscillators employ six OTAs. Each class has 32 different forms, resulting in 128 Wien oscillators using OTAs. Having used grounded capacitors, the circuits are easy to be integrated and their parameters can be tuned electronically through tuning bias currents of the OTAs. The MULTISIM simulation results have been included to support the generation method.

On the systematic synthesis of OTA-based Wien oscillators

A new current-mode biquad-filtering circuit with single input and multi-outputs based on operational transconductance amplifier (OTA) is presented using three OTAs, two grounded capacitors and one grounded resistor, it can simultaneously realize second-order lowpass, bandpass, highpass, notch and allpass filters. The characteristic parameters can be adjusted orthogonally by a bias current of OTA and all capacitors are gounded. Morever, the circuit enjoys low sensitivities.

Li Tao

Papers

A new OTA-C current-mode biquad filter with single input and multiple outputs