B. L. Hart

Oxford Brookes University, Oxford, England, United Kingdom

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Publications (36)13.22 Total impact

  • M. Ben-Esmael · B. L. Hart · K. Hayatleh · F. J. Lidgey
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    ABSTRACT: An exemplary design demonstrates how to extend the common-mode rejection ratio (CMRR) bandwidth of a CMOS differential amplifier. The design presented uses MOSFETs with a channel length of 180 nm. A novel circuit technique is employed that partially compensates for the output capacitance of the tail current sink, thereby more than quadrupling the CMRR bandwidth in the example considered.
    No preview · Article · Oct 2014 · AEU - International Journal of Electronics and Communications
  • M. Ben-esmael · F. J. Lidgey · K. Hayatleh · B. L. Hart
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    ABSTRACT: The cascode amplifier has the potential of providing high gain and high bandwidth simultaneously. However, the design is not as intuitive as one might at first think. In this paper, we present a detailed analysis of the single cascode amplifiers. The relationship between gain and bandwidth is important. When used to achieve maximum bandwidth the voltage gain of the common-source stage is close to unity. However, when the cascode is designed to obtain a high voltage gain, then the gain-bandwidth trade-off, typical in the common source amplifier, reappears. This analysis is used to provide the basis for practical cascode amplifier design.
    No preview · Article · Mar 2013 · Journal of Circuits System and Computers
  • K. Hayatleh · N. Terzopoulos · B.L. Hart
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    ABSTRACT: A new technique is proposed for the design of a current source, in bipolar technology, with a very high output resistance and low output capacitance. Such a technique is useful in electrical impedance tomography applications. The DC relationships of the basic topology are established. Then, based on the analysis of a simplified equivalent circuit, an expression is formulated for the output resistance and tested against simulation results for both ideal and practical biasing circuits. The effect of circuit capacitances, and in particular, the role of the collector-base capacitance of the output transistor, in determining the output impedance as a function of frequency is considered. Finally, a new circuit is shown to have an incremental output resistance exceeding 200 GΩ.
    No preview · Article · Dec 2012 · International Journal of Electronics
  • M. Mathew · B.L. Hart · K. Hayatleh
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    ABSTRACT: The theoretical background and a selection of simulated results are presented for a 10 µA PTAT current generator that is a modified CMOS version of an existing bipolar configuration. Using standard 0.35 µm CMOS technology, the circuit exhibits a current variation of less than 0.01% when the supply rail voltage is changed from 0.5 to 10 V.
    No preview · Article · Nov 2012 · International Journal of Electronics
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    ABSTRACT: The cascode amplifier has the potential of providing high gain and high bandwidth simultaneously. However, the design is not as intuitive as one might at first think. In this paper we present a detail analysis of the single cascode amplifiers. The relationship between gain and bandwidth is important. When used to achieve maximum bandwidth the voltage gain of the common-source stage is close to unity. However when the cascode is designed to obtain a high voltage gain, then the gain-bandwidth trade-off, typical in the common source amplifier, re-appears. This analysis is used to provide the basis for practical cascode amplifier design.
    No preview · Conference Paper · Jan 2012
  • M. Mathew · B. L. Hart · K. Hayatleh · F. J. Lidgey
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    ABSTRACT: Operating from a 1 V rail supply, a proposed CMOS current-controlled DC current generator can function as a repeater, attenuator or amplifier over the input current range, 1 µA to 1 mA, with a current-transfer ratio accuracy better than 1% using IBM technology, characterised by a process with a 0.13 µm minimum feature size. In repeater mode, the incremental output resistance exceeds 30 MΩ for an output current of 500 µA at an output voltage of 0.20 V, and exceeds 1 MΩ for an output current of 1 mA at an output voltage of 0.22 V. For zero input current, the circuit dissipation is 117 µW.
    No preview · Article · Aug 2011 · International Journal of Electronics
  • M. Mathew · K. Hayatleh · B. L. Hart
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    ABSTRACT: This paper describes the design of a high-transconductance, wide-band, temperature-insensitive bipolar differential voltage-to-current converter, the transconductance of which is determined by a chosen degeneration resistor. Detailed illustrations of current and voltage traces are included to clarify circuit operation. Comparison with previously published designs shows that this converter provides better linearity, with very low temperature sensitivity and excellent transconductance predictability. Simulation results show that the proposed circuit, with a nominal transconductance of 5mS, has a Total Harmonic Distortion (THD) better than −70dB at 10MHz, with a degeneration resistor of 400 Ω over an input voltage range of 350mV for supply voltages of ±2.5V. The analysis and simulation comparisons are in good agreement. KeywordsTransconductance-Voltage-to-current converter-Total harmonic distortion-Global feedback-Emitter degeneration
    No preview · Article · Dec 2010 · Circuits Systems and Signal Processing
  • Khaled Hayatleh · Amr A. Tammam · Bryan L. Hart
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    ABSTRACT: The output characteristics of the basic current feedback operational amplifier (CFOA) in the linear region, on open-loop, would not appear to have been treated in the literature. This is possibly because it is not straightforward to determine, the problem being that the output saturates without the closed-loop connection. This paper considers a theoretical discussion that explains the results of simulation.
    No preview · Article · Dec 2010 · AEU - International Journal of Electronics and Communications
  • C. M. Chen · K. Hayatleh · B. L. Hart · F. J. Lidgey
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    ABSTRACT: This article presents a proposed modified flipped voltage follower for applications in a wideband MOSFET differential V/I converter using IBM 0.13 μm technology. Operating with ±2.5 V supply rails, the transconductance is nominally 3.3 mS for an input differential signal voltage range of 0.5 V, and the −3 dB bandwidth exceeds 4 GHz. The THD measured at 1 MHz for a differential input signal of 500 mVp-p is less than –82 dB, and is still below –50 dB at 1 GHz.
    No preview · Article · Apr 2010 · International Journal of Electronics
  • Khaled Hayatleh · Amr A. Tammam · Bryan L. Hart
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    ABSTRACT: The input stage design in current-feedback operational amplifiers (CFOAs) is primarily responsible for determining the performance of the amplifier, including input voltage range, input referred offset voltage and DC input current. This paper focuses on analysis of the input stage of the conventional CFOA. The outcome of the work gives clear insight into the operation of the CFOA and establishes the mechanisms responsible for determining these parameters.
    No preview · Article · Apr 2010 · AEU - International Journal of Electronics and Communications
  • R. Wu · F. J. Lidgey · K. Hayatleh · B. L. Hart
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    ABSTRACT: A novel circuit design technique is presented which improves gain-accuracy and linearity in differential amplifiers. The technique employs negative impedance compensation and results demonstrate a significant performance improvement in precision, lowering sensitivity, and wide dynamic range. A theoretical underpinning is given together with the results of a demonstrator differential input/output amplifier with gain of 12 dB. The simulation results show that, with the novel method, both the gain-accuracy and linearity can be improved greatly. Especially, the linearity improvement in IMD can get to more than 23 dB with a required gain. Copyright © 2009 John Wiley & Sons, Ltd.
    No preview · Article · Jan 2009 · International Journal of Circuit Theory and Applications
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    ABSTRACT: This paper presents a novel voltage-follower, implemented in bipolar technology, based on a global feedback technique. The evaluation of the circuit has been carried out using extra fast complimentary transistors and the biasing circuitry followed the same design philosophy. The proposed design exhibits very high input and very low output impedance, due to the feedback technique, for operating frequencies beyond 1GHz. The small-signal bandwidth achieved is higher than 3GHz, the output voltage swing is some ±3.2V, the offset voltage is around 200uV while the input offset current is just above 130nA. The new circuit achieved gain flatness to within 0.1dB up to 170MHz, featuring total harmonic distortion better than -65dB and intermodulation distortion of around -70dB, for capacitive loads up to 10pF. The operation of the novel design is specified from -20°C to +100°C and the power dissipation is some 52mW on a ±5V power supply.
    Full-text · Conference Paper · Dec 2008
  • R. Wu · R.F.J. Lidgey · K. Hayatleh · B.L. Hart
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    ABSTRACT: Design of differential amplifier with high gain accuracy and high linearity is presented in the paper. The amplifier design is based on the negative impedance compensation technique reported by the authors in [1]. A negative impedance with high precision, low sensitivity, wide input signal range and simple structure is used for the compensation of differential amplifier. Analysis and simulation results show that gain accuracy and linearity can be improved significantly with the negative impedance compensation.
    No preview · Conference Paper · Jun 2008
  • M. Mathew · K. Hayatleh · B.L. Hart · F.J. Lidgey
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    ABSTRACT: This paper describes a highly linear and low- distortion, bipolar differential voltage-to-current converter (V-I) circuit that can be used for a number of applications, such as the transconductance stage for mixer circuits and gm-c filter circuits. This circuit is capable of providing a wider linear range of operation and lower total harmonic distortion compared with the conventional emitter-degenerated emitter-coupled differential pair due to the global feed-back technique used. Simulation results show that this circuit can provide 30dB improvement in total harmonic distortion over an operating range from -0.5V to +0.5V. This circuit uses a supply voltage of plusmn2.5V and an emitter degeneration resistor of 600 Omega.
    No preview · Conference Paper · Apr 2008
  • B.L. Hart · K. Hayatleh · F.J. Lidgey
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    ABSTRACT: This paper describes the design of a DC voltage-to-current converter (V-I) which is unique in that, operating from a single positive supply rail, it produces an output current linearly related to an input voltage down to an input voltage of zero. Simulation results, presented for operation over a DC input range from zero to 100mV, are in very close agreement with those predicted by the theory presented.
    No preview · Conference Paper · Apr 2008
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    ABSTRACT: A popular form for a voltage-follower (VF) with global feedback is a voltage operational amplifier (Op-Amp) with 100% negative feedback. Nevertheless, with currently available Op-Amps it is unable to meet high frequency specifications. This paper presents a high frequency voltage-follower based on an overall feedback technique. Despite the global feedback loop, the design presented small-signal bandwidth higher than 3GHz and gain flatness to within 0.1dB up to 170MHz. Due to this feedback loop, the circuits exhibits very high input and very low output impedance. In addition, the output voltage swing achieved is some ±3V, with an input offset current of around 130nA and an offset voltage in the range of 200uV. The proposed circuit is very stable, due to the stability technique used, maintaining low distortion. The total harmonic distortion (THD) of the circuit is better than -65dB and the intermodulation distortion (IMD) is some -70dB, for capacitive loads up to 10pF. The analysis of the novel circuit has been carried out for operating temperatures from -20 o C to +100 o C, using Analog Devices' extra fast complementary transistors. The power dissipation is some 52mW on a ±5V power supply, although it can be reduced to ±3.3V, without affecting significantly the performance, depending on the application.
    Full-text · Article · Jan 2008
  • K. Hayatleh · A. A. Tammam · B. L. Hart · F. J. Lidgey
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    ABSTRACT: The operation of the conventional current feedback operational amplifier (CFOA) is reviewed and its performance parameters used as benchmarks in the development of a new input stage architecture that provides a common-mode rejection ratio (CMRR) improvement of some 45 dB and offset voltage less than 10 mV.
    No preview · Article · Dec 2007 · International Journal of Electronics
  • M. Mathew · K. Hayatleh · B.L. Hart · F.J. Lidgey
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    ABSTRACT: This paper considers two schemes in which negative feedback is applied to a conventional emitter-coupled differential voltage-to-current converter circuit in order to achieve lower distortion. Representative circuits for each of these schemes together with simulated results for a given value of emitter-degeneration resistor are presented. It is possible to achieve a reduction in total harmonic distortion (THD) exceeding 20dB, for a peak-to-peak differential input voltage of 500mV, over that possible without this feedback.
    No preview · Conference Paper · Sep 2007
  • M. Mathew · K. Hayatleh · B.L. Hart · F.J. Lidgey
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    ABSTRACT: The use of two complementary emitter-followers, in which the collector currents are held effectively constant by feedback action, facilitates the design of a differential voltage- current converter capable of producing lower output signal distortion. The proposed circuit provides an extended linear operating range, and total harmonic distortion (THD) 20 dB better than that compared with an emitter-degenerated long- tailed pair circuit. Simulation results show that the THD is better than -70 dB for differential input signals up to 0.5 V at a test frequency of 1 MHz and supply voltage of plusmn5 V.
    No preview · Conference Paper · Aug 2007
  • K. Hayatleh · A. A. Tammam · B. L. Hart
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    ABSTRACT: This paper considers the trade-offs involved in the design of six new input stages intended to improve the performance of a current feedback operational amplifier (CFOA), over that possible using an established input circuit configuration, with respect to three major characteristics, viz, common mode rejection ratio (CMRR), offset voltage and slew-rate.
    No preview · Article · Feb 2007 · Analog Integrated Circuits and Signal Processing