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A new complementary metal-oxide-semiconductor transadmittance-mode with input voltage and output current, analogue non-linear odd-function synthesiser is presented. The proposed circuit is based on the assumption that a non-linear odd- function can be approximated by the summation of hyperbolic tangent (tanh) functions with different arguments. Each term of the tanh function expansion is realised by exploiting to advantage the inherent non-linearity of a current-controlled current-conveyor (CCCCII) (or an operational transconductance amplifier (OTA)) with a different bias current. The output currents of these CCCCIIs (OTAs) are weighted using the gains of current amplifiers. These weighted currents are algebraically added to form the required non-linear function. The proposed circuit is suitable for integration, can be easily extended to include higher order terms of the tanh-odd-function expansion and can be programmed to realise arbitrary hard non-linear odd-functions that cannot be easily reali...

This paper presents four new topologies for emulating floating immittance functions. Each circuit uses two or three current-feedback operational-amplifiers (CFOAs) and three passive elements. The proposed topologies can emulate positive/negative lossless and lossy floating inductances, and positive/negative capacitance, resistance and inductance multipliers in addition to floating frequency-dependent positive and negative resistances. The functionality of the proposed circuits is verified using the Advanced Design System software and the AD844 CFOA. The simulation results are in excellent agreement with the theoretical calculations.

Over the years researchers have developed and reported a huge number of sinusoidal oscillator circuits and classified them, according to the tunability of their frequencies of oscillation, as enjoying independent control of the frequency and condition of oscillation. This classification is based on obtaining the frequency and the condition of oscillation using the Barkhausen criterion. This article serves as a caution as it appears that this classification is incorrect. Experimental and SPICE simulation results that support this caution are included.

This article presents a simple mathematical model for the output-voltage/input-voltage characteristics of the carbon nanotube field-effect transistor (CNTFET)-based and the single-electron tunnelling transistor (SET)-based inverting amplifiers. The model, basically a Fourier-series, yields closed-form expressions for the amplitudes of the harmonic and intermodulation components of the output voltage resulting from a multisinusoidal input voltage. The special case of a two-tone equal-amplitude input signal is considered in detail. The results show that the harmonic and intermodulation performance of the CNTFET-based and SET-based inverting amplifiers is strongly dependent on the values of the bias voltage and the amplitudes of the input tones. Moreover, the results show that for the CNTFET-based inverting amplifier, either the relative second-order or the relative third-order intermodulation component is dominant, while for the SET-based inverting amplifier, the relative third-order intermodulation is alwa...

Large signal analysis of mixers excited by three tone signals is presented. The special case of two equal-amplitude sinusoids plus a difference-frequency injection is considered in detail and the results are compared, whenever possible, with previously published results. Contrary to previously published results, it is shown that even under large signal conditions and strong nonlinearity it is possible, at least in theory, to totally eliminate the third-order intermodulation when the amplitudes of the equal-amplitudes input sinusoids and the difference-frequency injection are equal.

A CMOS integratable current-mode analogue function synthesiser circuit is presented. The proposed circuit is based on approximating the required function using its sixth-order Taylor series expansion. These approximations can be implemented by adding the weighted output currents of a number of basic building blocks, built around a basic current squarer, and a constant current. The proposed circuit can simultaneously realise 32 different mathematical functions and can be easily expanded to accommodate many others. SPICE and Monte Carlo simulation results demonstrating the circuit performance are included.

In this article, the design of configurable analogue blocks for field programmable analogue arrays is presented. The configurable blocks are capable of performing integration, differentiation, amplification, log, anti-log, add and negate functions. The realisation of these functions depends on differential continuous-time current-mode translinear loop techniques. To maintain high frequency operation, the programmability and configurability of the blocks are achieved by modifying the block's biasing conditions digitally. Simulation results for the presented circuits are included.

A new technique for predicting the harmonic and intermodulation performances of class-AB stages is presented. The proposed technique is based on modelling the transfer characteristic of the class-AB stage using a Fourier-series approximation. The number of terms of the Fourier-series is decided based on the required accuracy and the coefficients of the series are obtainable using simple hand calculations. The results obtained are in excellent agreement with simulation results and confirm that the intermodulation performance is dominant compared to the harmonic performance.

Large signal analysis of a wideband non-linear amplifier excited by a multisinusoidal signal is presented. The special cases of two equal-amplitude sinusoids and their injected harmonics, sum- and difference-frequency components are considered in detail and the results are compared, whenever possible, with previously published simulation and experimental results.

This paper presents a core cell that can be reconfigured and combined with current mirrors to implement exponential, logarithmic, multiplier, divider and raise-to-power function circuits. The proposed circuit uses CMOS transistors operating in the strong inversion. The proposed circuits has been verified with the 0.8 µm CMOS technology by HSPICE simulations. The simulations results confirm the functionality of the proposed circuits. The proposed circuits paves the way for designing analog signal processors.

A new electronic interface circuit is presented. The circuit is built around a single plus-type second-generation current conveyor (CCII+) and can be used with resistive, capacitive and resistive-capacitive sensors. Experimental results are provided.

A novel mixed-mode biquad circuit is presented. The circuit uses six single-output- and one dual-output-operational transconductance amplifiers, two grounded capacitors; and can realize lowpass, highpass, bandpass, notch, lowpass-notch, highpass-notch and allpass responses from the same topology. The circuit can be driven by voltage or current and its output can be voltage or current. The parameters ωo and ωo/Q o enjoy independent electronic tunability. Simulation results are included.

Analytical expressions are obtained for the amplitudes of the desired output components of a SiGe translinear harmonic mixer excited by large-amplitude local oscillator and radio-frequency signals. Comparison with previously published calculated and simulated results is included.

A new CCII-based circuit for the simulation of mutually coupled circuits is presented. The circuit uses six commercially available plus-type second-generation current conveyors (CCII+s), six resistors and two grounded capacitors. The primary self-inductance, the secondary self-inductance and the mutual inductance can be independently controlled using three different resistors. SPICE simulation results are included.

A new circuit approach for realizing analogue synthesizers of a wide range of special functions is proposed. The proposed technique is based on approximating a special function using exponential approximations. The circuit is flexible and can be programmed to produce a wide range of special functions with reasonable accuracy. The proposed circuit uses transistors, resistors, switches and current sources and is suitable for integration. Simulation results obtained from the synthesis of the error function erf(x), the sine integral Si(x), the sinh integral Shi(x), the integrals of the Struve function , and the modified Struve function , are presented.

A new dual-slope triangular/square wave generator is presented. The circuit uses few active and passive components and can be easily integrated. Experimental results obtained from a breadboard implementation, using discrete transistors, show that by using a grounded resistor the frequency of oscillation can be tuned in the range 1.7 kHz-3.5 kHz without disturbing the slopes the positive-going and the negative-going edges of the triangular wave.

A new mixed-mode biquad circuit is presented. The circuit uses six single-output plus-type second-generation current-conveyors (CCII+s), a single dual-output CCII+, two grounded capacitors, eight resistors, at least two of them permanently grounded, and can realize lowpass, highpass, bandpass, notch, lowpass notch, highpass notch and allpass responses from the same topology. The circuit can be driven by voltage or current and its output can be voltage or current. The parameters ω0 and ω0/Q 0 enjoy independent electronic tunability. Simulation results are included.

A new technique for designing a sinusoidal frequency divider/multiplier is presented. The technique uses current-mode devices: plus-type second-generation current conveyor, translinear full-wave current rectifier, translinear current amplifier and operational transconductance amplifiers. The division/multiplication factor can be any integer or non-integer real number and can be controlled using currents. SPICE simulation results obtained for different values of the division/multiplication factor are included.

New expressions, in terms of the ordinary and modified Bessel functions, are presented for the amplitudes of the output harmonic and intermodulation products of the Darlington composite bipolar junction transistor excited by a multisinusoidal input voltage. SPICE simulation results confirming the presented theory are included.

A new circuit for generating ASK/FSK/PSK/QAM waves is proposed. The proposed circuit is built around a multiple-output current-controlled current-conveyor and a number of digitally controlled switches. Simulation results which confirm the validity of the circuit are included.

This paper discusses the large signal performance of CMOS analogue-functional elements. Fourier-series approximations are obtained for the transfer functions of the basic building blocks such as the linear CMOS transconductance element and the CMOS full-wave rectifier. Using these Fourier-series approximations, simple closed-form analytical expressions are obtained for the amplitudes of the harmonics at the output of a basic building block excited by a sinusoidal input signal. The analysis shows that, while the performance of the basic building blocks is near ideal at relatively small input amplitudes, performance degradation increases as the input amplitudes increase. On the other hand, since these expressions ignore the distortion mechanisms resulting from body effect and channel-length modulation, they cannot reliably predict the performance at small input signal levels. It appears, therefore, that body-effect and channel-length modulation must be taken into consideration for small-signal analysis.

This paper discusses the large signal performance of low-voltage analogue functional elements built around MOS field-effect transistors (MOSFETs). Fourier-series approximations are obtained for the transfer characteristics of the basic building blocks; such as the balanced source-coupled pair, the unbalanced source-coupled pair with different transistor sizes, the source-coupled pair with bias offset and the squaring circuits. Using the Fourier-series approximations of these basic building blocks, closed-form expressions are obtained for the amplitudes of the harmonics and intermodulation products at the output of analogue functional elements; such as the basic differential pairs, half-wave rectifiers, full-wave rectifiers and multipliers excited by a multisinusoidal input signals. Using these expressions comparison between the large signal performance of analogue functional elements can be performed and the parameters required for a predetermined performance can be determined.

The current controlled current-mode amplifier proposed by Fabre et al. (1996, IEEE Transactions on Circuits and Systems—I, 43, 82) is reanalysed to show that it can work not only under small signal conditions, as suggested by Fabre et al., but also under large signal conditions. Simulation results which confirm the theory presented are included.

A new circuit configuration is presented for synthesizing nonlinear functions. The proposed circuit is based on approximating the required function using a Taylor series. The terms of the resulting Taylor series are realized one-by-one, each in a separate building block, and the required function is the sum of the output currents of these blocks. The weights of the Taylor-series terms are controlled using current sources. The circuit is flexible and can synthesize any nonlinear function, to any degree of accuracy, once its Taylor-series approximation is obtained. The proposed circuit uses only bipolar transistors and current sources and is, therefore, very attractive for integration. Simulation results obtained from the synthesis of the ordinary Bessel functions J0(x)and J1(x), and the sine function sin(x) are presented.

A universal active biquad using the four-terminal floating nullors (FTFNs) is presented. The proposed circuit uses two FTFNs, two capacitors and two resistors. The proposed circuit has two input currents and can provide two highimpedance output currents. Without changing the circuit topology, the output currents can realize lowpass, highpass, bandpass, and allpass transfer functions. A notch transfer function can be obtained by adding a voltage-to-current converter using an additional FTFN. The proposed circuit enjoys low passive sensitivities and orthogonal tuning of the parameters ωo and ωo/Qo.

The nonlinear behaviour of the CMOS buffer stages, the single-stage complementary source follower and the complementary source follower cascade are analysed. Closed-form expressions are obtained for the harmonic and intermodulation components resulting from a multisinusoidal input signal. These expressions can be used to predict the limiting values of the input current for a prespecified tolerable distortion percentage.

A new technique for designing sinusoidal frequency multipliers is presented. The technique exploits the translinear principle and uses only bipolar junction transistors and current mirrors. The proposed technique results in simple, programmable and flexible frequency multiplying circuits fully compatible with silicon integrated circuit technology. Simulation results obtained from a tripler and a quadrupler are included.

A new current-mode multi-function filter is proposed. The filter uses only two operational amplifiers, four operational trans-conductance amplifiers (OTAs) and one multiple-output third-generation current-conveyor (CCIII±). Without using any external passive elements, lowpass, highpass, bandpass, notch and allpass responses can be realized without changing the circuit topology and without any matching or cancellation conditions. The parameters ωo and ωo/Qo, can be electronically tuned by adjusting the bias currents of the OTAs. The proposed circuit enjoys low sensitivities.

New current-mode current-controlled filters are proposed. The proposed realization requires three dual-output positive/negative-type current-controlled current conveyors (CCCII±) and can simultaneously realize low-pass, high-pass and band-pass responses. Realization of notch and all-pass responses is feasible. The parameters ω0, ω0/Q0 and the band-pass gain can be controlled by adjusting the bias currents of CCCIIs. The proposed realizations enjoy low sensitivities.

This brief communication is a comment on the paper Current-mode quadrature sinusoidal oscillator using single FTFN

A simple current-mode analogue multiplier/divider circuit using only two secondgeneration current-controlled current-conveyors is presented. No resistors, no capacitors and no MOS transistors are required. The circuit can perform multiplication and division without changing its topology. Results obtained using SPICE simulation are included.

A new CFOA-based triangular/square wave generator is presented. The circuit uses one CFOA, two grounded resistors, one floating resistor and one grounded capacitor. The feasibility of obtaining linearly voltage controlled oscillation is explored. Experimental results are included.

Two new grounded capacitor CCII-based sinusoidal oscillator circuits, with independent frequency control, are presented. The circuits exploit, to advantage, the internal pole of the CCII. The experimental results show that high frequencies of oscillation can be obtained with only one externally connected capacitor.

The nonlinear behaviour of the mixed translinear loop is analysed. Closed-form expressions are obtained for the harmonic and intermodulation components resulting from a multisinusoidal input signal. These expressions can be used to predict the limiting values of the input current for a prespecified tolerable distortion percentage.

Novel CFOA-based sinusoidal oscillator circuits are presented. Two of the proposed circuits enjoy independent control of the frequency of oscillation and the condition of oscillation. Experimental results are included.

A novel sinusoidal oscillator circuit using the current-feedback operational amplifier (CFOA) is presented. The circuit uses one CFOA and four passive elements only and enjoys independent control of the frequency of oscillation and the condition of oscillation. Experimental results are included.

A new universal voltage-mode second-order filter circuit is presented. The circuit has three inputs and one-low-impedance output and can realize all the standard filter functions; lowpass, highpass, bandpass, notch and allpass, without changing the passive elements. The proposed circuit uses only five passive components and enjoys independent control of the natural frequency and the bandwidth, and orthogonal control of the natural frequency and the quality factor as well as low active and passive sensitivities.

An improved analysis for the bipolar linear transconductor, assuming a finite value for the transistor current-gain β, is presented. A new expression for the normalized input-voltage as a function of the normalized output-current is obtained. A Fourier-series model is presented for this current-voltage relationship. Closed-form expressions are also derived for the harmonic and intermodulation components resulting from exciting the bipolar linear transconductor by a multisinusoidal input voltage. These expressions can be used to predict the limiting values of the input voltage amplitudes for a prescribed tolerable distortion percentage.

Two novel schemes are presented for realizing operational transconductance amplifier (OTA)-based current-controlled grounded inductors. While the use of OTAs yields a wide range of electronic tunability, the schemes are temperature insensitive. Experimental results confirming the theory are presented.