Electronically tunable versatile voltage-mode universal filter

Department of Electronic Engineering, De-Lin Institute of Technology, Taiwan, ROC
AEU - International Journal of Electronics and Communications (Impact Factor: 0.6). 04/2008; 62(4):316-319. DOI: 10.1016/j.aeue.2007.04.008


A novel electronically tunable versatile voltage-mode universal biquad filter by using two single-output-operational transconductance amplifiers (OTAs), one differential difference current conveyor (DDCC) and two capacitors is proposed. The proposed circuit, which can be used as either a four-input single-output universal filter or a single-input three-output multifunction filter with the same topology. Besides, the new circuit offers the following advantageous features: realization of all the non-inverting and inverting biquadratic filter signals from the same configuration, no need to employ inverting-type input signals, no need to component-matching conditions and low passive sensitivity performance.

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    • "However, from our investigations, there are seen that the voltage-mode oscillators and filters reported in the previous literatures [3-18] require too many components. In addition, each circuit can work only one function, either universal biquad filter [3] [4] [5] [6] [7] [8] [9] [10] [11] or oscillator [4-18]. Very few voltage-mode circuits are available in the literatures [19] [20] [21] which can be used as both filters and oscillators. "
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    ABSTRACT: In this paper, a circuit employing current controlled current conveyor trans-conductance amplifiers (CCCCTAs) as active element is proposed which can function both as biquad filter and oscillator. It uses two CCCCTAs and two capacitors. As a biquad filter it can realizes all the standard filtering functions (low pass, band pass, high pass, band reject and all pass) in voltage-mode and provides the feature of electronically and orthogonal control of pole frequency and quality factor through biasing current(s) of CCCCTAs. The proposed circuit can also be worked as oscillator without changing the circuit topology. Without any resistors and using capacitors, the proposed circuit is suitable for IC fabrication. The validity of proposed filter is verified through PSPICE simulations.
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    • "In our work it is proved that three outputs are sufficient for universal filter design. Using a pair of OTAs and single VM differential difference current conveyor (DDCC) as universal filter is given in [20]. This is indeed an interesting network but its proper function is a question since there are no simulations or measurements. "
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    ABSTRACT: 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.
    Radioengineering 09/2009; 18(3):285-294. · 0.65 Impact Factor
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    ABSTRACT: In this paper, a novel versatile active building block the differential-input buffered and transconductance amplifier (DBTA) is proposed. The application of the newly defined active function block is shown on the design of voltage-mode (VM), multi-input and single-output (MISO)-type multifunction biquad, employing single DBTA and five passive elements. Proposed VM filter structure can realize four filter functions i.e., low- (LP), band- (BP), high-pass (HP) and band-stop (BS) without changing the circuit topology and enables independent control of the quality factor Q using single passive element. Theoretical results are verified by PSPICE simulations using a BJT realization of DBTA.
    IEICE Electronics Express 03/2009; 6(6-6):pp. 329-334.. DOI:10.1587/elex.6.329 · 0.32 Impact Factor
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