Light-Emitting Diodes. (Monographs in Electrical and Electronic Engineering.) By A. A. Bergh and P. J. Dean. Pp. viii+591. (Clarendon: Oxford; Oxford University: London, 1976.) £22.

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Light-emitting diodes

In the paper, an analysis of the state-of-the-art of active elements for analog signal processing is presented which support - in contrast to the conven tional operational amplifiers - not only the voltage-mode but also the current- and mixed-mode operations. Several pro blems are addressed which are associated with the utiliza tion of these elements in linear applications, particularly in frequency filters. A methodology is proposed which generates a number of fundamentally new active elem ents with their potential utilization in various areas o f signal processing.

Active Elements for Analog Signal Processing: Classification, Review, and New Proposals

Current conveyors and related current-mode circuits have begun to emerge as an important class of circuits with properties that enable them to rival their voltage-mode counterparts in a wide range of applications. The use of current rather than voltage as the active parameter can result in higher usable gain, accuracy and bandwidth due to reduced voltage excursion at sensitive nodes. A current-mode approach is not just restricted to current processing, but also offers certain important advantages when interfaced to voltage-mode circuits. The author sets out to survey developments in conveyors and current-mode circuits from both an historical and technical viewpoint and to act as a useful source of reference material.

Recent developments in current conveyors and current-mode circuits

Novel CMOS realisations of a differential voltage current conveyor (DVCC) are described. These circuits are powerful building blocks, especially for applications demanding differential or floating inputs like impedance converter circuits and current mode instrumentation amplifiers. Applications suitable for VLSI are then considered by using the DVCC to realise a MOS transconductor and a continuous-time current mode MOSFET-C filter. PSpice simulations indicate the excellent performance of the proposed DVCC and of its circuit applications.

Novel CMOS differential voltage current conveyor and its applications

The authors present a new versatile circuit building block called a differential difference current conveyor (DDCC). An IC technique for implementing the DDCC is also presented. The DDCC-based frequency-selective circuits and nonlinear building blocks such as multiplier, squarer and square rooter are developed. Experimental results are given to demonstrate the feasibility of the proposed techniques, and they show that DDCC-based circuits offer a competitive design choice to CCII-based and DDA-based circuits.

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CMOS differential difference current conveyors and their applications

An integrable circuit technique for implementing both positive and negative second-generation current conveyors (CCII) is described. Since the proposed circuits consist of a differential pair, current sources, and current mirrors, the realization method can result in a fully integrated current conveyor. The realization method is suitable for fabrication in CMOS technology. The performance of the CMOS-based CCIIs is discussed in detail. The basic performances are demonstrated and simulation and experimental results are presented. The DC transfer characteristics for converting resistors are linear over the total dynamic range. >

Accurate CMOS-based current conveyors

A novel current-controlled multiple-input single-output current-mode universal filter employing current differencing transconductance amplifiers (CDTAs) as active elements is described. The proposed circuit offers the following attractive features: employment of the minimum number of active and passive components; simultaneous realization of all the standard filtering functions; independent current-control of the parameters ω o and ω o / Q ; no requirement of component matching conditions; employment of only two grounded passive capacitors which is suitable for integrated circuit (IC) implementation; and low passive and active sensitivities. PSPICE simulation results are given to verify the theoretical analysis. An example application using the proposed circuit in cascade realization of the high-order current-mode filter is also presented.

Multiple-input single-output current-mode multifunction filter using current differencing transconductance amplifiers

A generalised current conveyor, termed an electronically tunable second-generation current conveyor (ECCII), whose current-transfer ratio can be varied by electronic means, is introduced. A method is proposed for realising ECCII in monolithic integrated form providing both a positive and a negative ECCII in the same circuit. Experimental and simulation results demonstrating the circuit performance are included. Some simple applications which show that their circuit property can be varied by electronic means are also presented.

Integrable electronically tunable current conveyors

A CMOS-based small signal current amplifier, which is constructed from two current-squaring circuits with improved dynamic range is introduced. A circuit technique for realising an integrable electronically tunable current conveyor that is designed around the current amplifier is proposed. >

CMOS-based electronically tunable current conveyor

A single-resistance-controlled quadrature oscillator circuit using current differencing buffered amplifiers (CDBAs) as active components is proposed. The proposed circuit is realised through the employment of two CDBAs, three resistors and two grounded capacitors. Outputs of two sinusoidal with 90° phase difference are available. The oscillation condition and the oscillation frequency of the proposed quadrature oscillator can be controlled independently by a single resistor. In comparison with the previously reported circuits, the proposed configuration considerably reduces the number of passive elements.

Wanlop Surakampontorn

Papers

Accurate CMOS-based current conveyors

Multiple-input single-output current-mode multifunction filter using current differencing transconductance amplifiers

Integrable electronically tunable current conveyors

CMOS-based electronically tunable current conveyor

Single-resistance-controlled quadrature oscillator using current differencing buffered amplifiers