www.ietdl.org Published in IET Circuits, Devices & Systems Received on 25th July 2008 doi: 10.1049/iet-cds:20080211
ISSN 1751-858X
COMMENT
Practical voltage/current-controlled grounded resistor with dynamic range extension Abstract: Recently, Maundy, Gift and Aronhime presented a voltage/current-controlled grounded resistor which makes use of bisection of the drain-to-source voltage of a FET to produce a linear resistor with wide dynamic range extension. The purpose of this communication is to bring on record, in the context of the above paper, our works on the same topic published more than a decade back which are closely related to the work reported in the above-mentioned paper but have not been cited therein.
In the above paper [1], a voltage/current-controlled grounded resistor was presented which makes use of bisection of the drain-to-source voltage of a FET to produce a linear resistor with wide dynamic range extension. A second generation positive current conveyor (CCIIþ) along with three resistors was used to extend the linearity of the variable resistance and two implementations were shown. Fig. 1 is realisable with a CCIIþ and a voltage follower [both realisable by a single current feedback op-amp (CFOA) AD844 which contains a CCIIþ and a voltage follower with the Z-pin of the CCIIþ taken out] but requiring a floating control voltage and Fig. 3 is realised with two CIIþ, one voltage follower, thus, necessitating two AD844-type CFOAs. The merits of the new circuits were compared with the Nay– Budak circuit (henceforth referred to as NB circuit) from Ref. [12] of the paper. The purpose of this communication is to bring on record, in the context of the above paper, our works [2–9] on the same topic published more than a decade back which are closely related to the work reported in the above paper but have not been cited therein. The works [2–9] extended the ideas contained in the work of Nay and Budak (Ref. [12] of the above paper) from the realisation of voltage-controlled resistances (VCR) to the domain of voltage-controlled impedances with wide dynamic range extension and employing the same principle for IET Circuits Devices Syst., 2008, Vol. 2, No. 5, pp. 465– 466 doi: 10.1049/iet-cds:20080211
nonlinearly cancellation as in the above paper (i.e. bisection of the drain-to-source voltage of a FET) and one of them [9] used exactly the same active devices, that is, CFOAs (AD844) as used in the above paper. A brief outline of the works reported in [2–9] is as follows. References [2, 3] presented two new op-amp-JFET configurations which not only realise VCRs but, unlike NB configuration, made it possible to realise voltage-controlled inductance (VCL) and voltage-controlled capacitance (VCC) elements too (in both positive and negative forms by two different circuits). A simpler configuration employing two unity gain amplifiers, four passive elements and a FET, exhibiting similar features, was presented in [4]. The configuration of [5] employed three op-amps but could realise voltage-controlled R, L, C, as well as voltagecontrolled (VC) FDNR (an element having Z(s) ¼ 1/Ds 2) and VC FDNC (an element having Z(s) ¼ Ms 2). The circuit of [6] was more versatile as it realised similar functions in both positive and negative forms while using only two op-amps. Reference [7] considered the realisation of floating linear VCR which lead to the evolution of a novel lowcomponent-count configuration making it possible to realise a floating as well as grounded VCR, both from the same structure, with exactly the same number of active and passive components, (i.e. a single op-amp, one FET and five 465
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www.ietdl.org resistors). It was shown in [9] that this circuit can also be realised by one CFOA (see Fig. 10 therein) thereby attaining relatively higher frequency range. A linear, floating, generalised VC impedance configuration using two operational mirrored amplifiers was presented in [8]. Two circuits (employing two CFOAs implemented from AD844, four passive components and a JFET) each of which can realise grounded VC impedances, that is, VCR, VCC and VCL and one circuit employing three CFOAs, four passive components and a JFET which can realise floating VCR, VCC and VC-FDNR elements were introduced in [9]. All the three AD844-based circuits of [9] employed bisection of the drain-to-source voltage of the FET used in non-saturation region like NB circuit and the circuits proposed in the paper quoted above. It may be mentioned that two of the VCR circuits of [9], employing BFW11 JFETs and AD844 CFOAs biased with +15 V DC power supplies, achieved a linear range as large as 15 V p– p without causing any noticeable distortion at the voltage output terminals of the CFOAs because of the fact that the FET inside both these circuits was required to handle only a small fraction of the applied input signal.
R. Senani1 D.R. Bhaskar2
References [1] MAUNDY B., GIFT S., ARONHIME P.: ‘Practical voltage/current controlled grounded resistor with wide dynamic range extension’, IEE Circuits Devices Syst., 2008, 2, (2), pp. 201– 206 [2] SENANI R., BHASKAR D.R.: ‘Realization of voltage-controlled impedances’, IEEE Trans. Circuits Syst., 1991, 38, (9), pp. 1081 – 1086 [3] SENANI R., BHASKAR D.R.: ‘Realization of voltage-controlled impedances’, IEEE Trans. Circuits Syst., 1992, 39, (2), p. 162 [4] SENANI R., BHASKAR D.R.: ‘A simple configuration for realizing voltage-controlled impedances’, IEEE Trans. Circuits Syst., 1992, 39, (1), pp. 52– 59 [5] SENANI R. , BHASKAR D.R. : ‘Versatile voltage-controlled impedance configuration’, IEE Proc., Circuits Devices Syst., 1994, 41, (5), pp. 414– 416 [6] SENANI R.: ‘Universal linear voltage controlled impedance configuration’, IEE Proc., Circuits Devices Syst., 1995, 142, (3), p. 208 [7] SENANI R. : ‘Realization of linear voltage-controlledresistance in floating form’, Electron. Lett., 1994, 30, (23), pp. 1909 – 1911
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[8] SENANI R.: ‘Floating GNIC/GNII Configuration realized with only a single OMA’, Electron. Lett., 1995, 31, (6), pp. 423– 425
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[9] SENANI R.: ‘Realization of a class of analog signal processing/signal generation circuits: novel configuration using current feedback op-amps’, Frequenz: J. Telecommun., 1998, 52, (9/10), pp. 196– 206
Division of Electronics and Communication Engineering, Netaji Subhas Institute of Technology, Sector-3, Dwarka, New Delhi 110078, India Department of Electronics and Communication Engineering, Faculty of Engineering and Technology, Jamia Millia Islamia, Jamia Nagar, New Delhi 110025, India E-mail:
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IET Circuits Devices Syst., 2008, Vol. 2, No. 5, pp. 465– 466 doi: 10.1049/iet-cds:20080211
