D.G. Haigh

Symbolic Framework for Linear Active Circuits Based on Port Equivalence Using Limit Variables

This paper proposes a new framework for linear active circuits that can encompass both circuit analysis and synthesis. The framework is based on a definition of port equivalence for admittance matrices. This is extended to cover circuits with ideal active elements through the introduction of a special type of limit-variable called the infinity-variable (infin-variable). A theorem is developed for matrices containing infin-variables that may be utilized in both circuit analysis and synthesis. The notation developed in this framework can describe nonideal elements as well as ideal elements and therefore the framework encompasses systematic circuit modeling

Control of circuit distortion by the derivative superposition method [MMIC amplifier]

The derivative structure of the characteristics of GaAs FETs naturally gives rise to changes in magnitude and reversals of phase of intermodulation distortion components. An MMIC design method that exploits the phase reversal to achieve control of distortion in an amplifier is presented. An example circuit is designed and its measured performance is compared with that of a conventional amplifier.

Admittance Matrix Models for the Nullor Using Limit Variables and Their Application to Circuit Design

A framework for symbolic analysis and synthesis of linear active circuits has previously been proposed which is based on the use of admittance matrices and infinity-variables. The notation has the important advantage that it can describe both ideal circuit elements, for which an infinite limit is implied, and nonideal circuit elements for which matrix elements are considered finite. The nullor is a very important circuit element because it can represent the ideal operational amplifier and the ideal transistor. For the nonideal case, the use of finite matrix elements implies that the operational amplifier and transistor are both modelled as a voltage-controlled current source, which is fine if the transistor is a field effect transistor or if the operational amplifier is of the transconductance type, but not otherwise. The purpose of this paper is to apply the infin-variable framework in order to derive alternative models for the nullor that can be used to model voltage, current and transresistance operational amplifiers and bipolar junction transistors. We also show that the infin-variable description of an ideal transistor can include a factor to represent transistor geometry

A Method of Transformation from Symbolic Transfer Function to Active- RC Circuit by Admittance Matrix Expansion

Active-RC circuits containing 2-terminal linear passive elements and ideal transistors or operational amplifiers are derived from symbolic voltage or current transfer functions by admittance matrix transformations without any prior assumption concerning circuit architecture or topology. Since the method is a reversal of symbolic circuit analysis by Gaussian elimination applied to a circuit nodal admittance matrix, it can generate all circuits using the specified elements that possess a given symbolic transfer function. The method is useful for synthesis of low-order circuits, such as those used for cascade implementation, for deriving alternative circuits with the same transfer function as an existing circuit or for realizing unusual transfer functions, as may arise, for example, where a transfer function is required that contains specific tuning parameters

Low-distortion MMIC power amplifier using a new form of derivative superposition

Reduction of interchannel interference produced by a power amplifier near 1-dB compression is a key concern for the wireless communications industry. In this paper, we present a 100-mW monolithic-microwave integrated-circuit (MMIC) power amplifier designed using a novel form of the derivative superposition method. The measured results of the MMIC power amplifier showed a two-tone carrier-to-interference (C/I) ratio of 45 dBc with an efficiency of 22.5% when backed off by 4.5 dB from the 1-dB compression point. We demonstrate that the MMIC power amplifier represents a good compromise between C/I ratio, output power, efficiency, and gain at the cost of an increase in total gate width, by comparing it to class-A, class-AB, and class-B single field-effect-transistor amplifiers.

Design and applications of single-path frequency-translated switched-capacitor systems

Single-path frequency-translated (SPFT) switched-capacitor (SC) systems have been previously proposed for the realization of highly selective bandpass filters with relative bandwidths below 1%. After examining in more generality the design constraints of such SPFT SC systems, novel solutions for the implementation of the decimator and interpolator architectures using an efficient combination of finite-impulse response, and infinite-impulse response SC circuits are presented. Several areas of application of SPFT SC systems, namely for filtering with programmable Q-factor and for single-sideband generation and detection are demonstrated. Detailed measured results, both in the frequency domain and in the time domain, are presented to illustrate the viability and performance of SPFT SC systems with the various operating modes. >

Design optimization and testing of a GaAs switched-capacitor filter

The design of GaAs MESFET technology is discussed. The design techniques developed are illustrated by means of a second-order switched-capacitor bandpass filter designed to operate at a switching frequency of 500 MHz. The design incorporates an operational amplifier architecture with a simulated gain of 60 dB and a switch driver circuit. Amplifiers are characterized in terms of settling time performance, and a general procedure for optimization of the switched-capacitor circuit to maximize switching frequency is presented. Measurements on a fabricated chip confirm the design of the filter and its components. >

Systematic synthesis method for analogue circuits. Part I. Notation and synthesis toolbox

This paper and its companion papers (subtitles Part II and Part III) together present a systematic synthesis method for analogue circuits. This paper presents an admittance matrix representation for the ideal nullor, the conversion of transmission matrices of useful circuit functions to admittance matrix form and a number of transformations needed for synthesis. The other papers illustrate the synthesis method through examples.

Novel circuit synthesis technique using short channel GaAs FETs giving reduced intermodulation distortion

We present graphically a novel FET synthesis technique based on the derivative structure observed in real GaAs MESFETs. The synthesis allows the generation of continuously differentiable linear or nonlinear transfer characteristics.

Synthesis of transconductor/multiplier circuits for gallium arsenide technology

A class of circuits is defined having transconductor/multiplier type response functions, which can be synthesized by making use of the square-law drain current versus gate-source voltage characteristic of depletion-mode gallium arsenide MESFETs, and which includes generalized transconductors and multipliers as special cases. Implementation is based on a general current differencing architecture in conjunction with voltage processing building blocks. The synthesis procedure presented generates a multitude of circuits, can allow equivalent circuits of alternative topology to be easily generated, and provides an increased understanding of different classes of transconductor/multiplier-type response functions and the relationship between these functions and circuit realizations. >