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Circuits, Devices and Systems, IEE Proceedings G

Issue 5 • Date Oct 1989

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Displaying Results 1 - 9 of 9
  • Function abstraction in automatic digital-circuit design

    Page(s): 235 - 244
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (744 KB)  

    A novel approach for automating the functional design of digital circuits is presented. The goal of digital-circuit design is to generate a workable and efficient design from high-level specifications. Function abstraction is an important step, whereas the specification of the target circuit is purely behavioural. It finds the essential functions of the desired behaviour. These functions can then be easily bound to physical modules. The design space for a behavioural description is huge. Therefore, it is important to have a powerful search strategy which will lead to a near optimum solution in reasonable time. The authors use the heuristic best-first search and meta-planning techniques to control the decision-making and optimise the final design. Experimental results are presented to compare the effectiveness of these search strategies. View full abstract»

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  • Novel switched-capacitor integrator for high-frequency applications

    Page(s): 263 - 267
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    A discrete integrator for switched-capacitor (SC) filter applications is developed. The proposed integrator is generated from an optimal linear combination of the lossless discrete integrator (LDI) and the bilinear discrete integrator, and therefore it is called the composite discrete integrator (CDI). This integrator is ideal for high-frequency applications because it doubles the normal folding frequency and minimises high-frequency discrete integrator errors. Several SC realisations of the CDI are given. SC circuits for emulating general first- and second-order analogue filter sections based on the CDI are also given. View full abstract»

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  • Characterisation of a phase-sensitive detector

    Page(s): 285 - 292
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    The phase-sensitive detector (PSD) operating particularly as a synchronous rectifier has an important role in many benchtop instruments, typical of which is the modern LCR component meter. The performance of the PSD determines the accuracy and frequency range of the overall instrument. Its characterisation by direct methods is particularly difficult to achieve by virtue of the necessity for an accurate knowledge of the relative phase between sine and switching waveforms at the PSD. The authors offer an alternative approach to characterisation of the PSD that circumvents the need for direct phase measurements. It calls for the use of a purpose designed sine-square generator which is relatively easy to achieve with today's technology. PSDs in the form of a buffered voltage-switching circuit and a track/hold circuit are examined in some detail. A statistical analysis is provided for the error bounds expected in the phase estimates. The work described can be readily adapted to improvements in phase measurement in existing LCR component meters. A technique called adaptive reference phase is introduced for this purpose. View full abstract»

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  • Analysis and modelling of initial delay time and its impact on propagation delay of CMOS logic gates

    Page(s): 245 - 254
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (548 KB)  

    The initial delay times due to the capacitive feedthrough effects in CMOS inverters are characterised and investigated. Based on the MOSFET large-signal model, the initial delay is modelled for a chain of CMOS inverters under step and ramp inputs. Optimal design that results in the minimum initial delay is obtained. Correlation between the initial delay and the propagation delay is constructed in the case of characteristic waveforms. The initial delays are found to determine the propagation delay. Applying the model to evaluate the speed performance of a scaled-down CMOS, the delay improvements for various scaling laws are compared. It is found that the most effective law in reducing the initial delay for internal circuits is the constant voltage law, whereas that for the input stage is the constant electric field law. Comparisons to SPICE simulation results are also given and good agreement is achieved. View full abstract»

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  • Characteristics of a coil wound with copper wire around YBaCuO superconductive thin wires

    Page(s): 279 - 283
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (236 KB)  

    YBaCuO superconductive thin wires were developed. Devices such as coils and transformers, where a copper wire is wound around these thin wires, have been trial manufactured. Attempts have been made to control the characteristics of these devices by supplying an electric current to these superconductive thin wires. View full abstract»

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  • Design of 2-D recursive digital filters with noncircular, symmetric cutoff boundary and constant group-delay responses

    Page(s): 255 - 259
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    The authors present a method of generating one-variable Hurwitz polynomial (HP) using the properties of the positive definite matrices coupled with resistance matrices. Also, they test the two-terms separable-denominator transfer function and three-terms separable-denominator transfer function for their effectiveness in the design of noncircular, symmetric two-D filters with constant group-delay specification. View full abstract»

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  • Thermal resistance of gallium-arsenide field-effect transistors

    Page(s): 229 - 234
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    The authors describe some thermal simulations for heat flow in gallium-arsenide field-effect transistors where the effects of surface metallisation and via holes are modelled. The results were found to be significantly different to those previously published, which were based on simpler physical models. The effects of surface metallisation were found to be important in modelling the thermal resistance, but the effects of via holes less so, using current technological limitations. View full abstract»

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  • Prime-factor Hartley and Hartley-like transform calculation using transversal filter-type structures

    Page(s): 269 - 277
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    The advances in digital fabrication technology have led to a new generation of integrated circuits capable of performing fast arithmetic operations, and opened the door to the consideration of algorithms that may be implemented with simple structures. When the number of data samples in the input block is prime or a product of primes, the Hartley transform can readily be mapped to circular convolutions and then implemented using transversal filter-type structures. Such a structure is simple and regular, and hence it is suitable for VLSI implementation. The Hartley transform is real-to-real and it is the same for both forward and inverse transformations. Hence, it is simpler and may therefore be somewhat faster than the DFT implemented by the same approach. View full abstract»

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  • Conduction in ohmic region of submicrometre MOSFET

    Page(s): 260 - 262
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (156 KB)  

    An accurate method to evaluate the variation of inversion charge along the channel, including the effect of lateral field from the source and drain, has been applied to find the current in the ohmic region of a submicrometre MOSFET. The model can explain the observed maximum in the normalised transconductance (gmL) as the channel length is reduced. The final rapid degradation of gmL is due to the overlapping of the depletion regions of the source and drain junctions. It is not necessary to assume an inhomogeneous surface state density. View full abstract»

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