Current-controlled Resistor Research Articles

INDEX AND SOLVABILITY OF UNCOUPLED CIRCUITS: A CHARACTERIZATION WITHOUT RESTRICTIONS ON THEIR PASSIVITY, TOPOLOGY OR CONTROLLING STRUCTURE

In this paper, we extend the topological formulae of Maxwell and Kirchhoff, characterizing the non-singularity of node-admittance and loop-impedance matrices, to mixed problems, that is, to circuits combining admittance and impedance descriptions or, in nonlinear cases, involving both voltage- and current-controlled resistors. By means of this mixed formula we analyze the index of differential-algebraic models of nonlinear uncoupled circuits in a very broad setting, namely, without assumptions on their topology, their passivity or the controlling variables for nonlinear resistors. In particular, our approach allows for a characterization of index two circuits in topologically degenerate settings, which had been so far elusive in the non-passive context. As a byproduct we address the unique solvability of mixed resistive circuits, a problem which also arises in connection to the so-called DC-solvability condition of dynamic circuits. For the sake of brevity, we discuss in less detail how to extend the analysis to problems with mixed descriptions in reactive devices.

Low‐component count BJT technology‐based current‐controlled tunable resistors and their applications

In this study, low-power and low-component count grounded and floating current-controlled tunable resistors are proposed. The validity of the proposed resistor circuits is demonstrated in two applications, second-order band-pass filter and negative inductor simulator circuit. To carry out the performance of the circuits, all the designed circuits are simulated through SPICE program by using real transistor models. Also, experimental results are included to confirm the theory. It is important to note that all the introduced circuit parameters and resistor values can be changed electronically by adjusting the values of dc control current sources only. Approximately four decades tunability range (from 34 Ω to 285 kΩ) and about 10 MHz bandwidth for the tunable resistors are achieved. In this tunability range, linear relationships between terminal currents and voltages are successfully obtained.

Circuit modeling and implementation of a biological neuron using a negative resistor for neuron chip

The implementation of a silicon neuron based on an OTA(operational transconductance amplifier) with a negative resistor for neuron chip is described. The proposed time-varying silicon neuron consists of a coupled oscillator representing the cell body and a current-controlled negative resistor with an input summing junction. SPICE (simulation program with integrated circuit emphasis) simulation results showed that a neuron pulse is generated above a threshold input current of 70 nA. In addition, we performed simulations of a three-neuron chain connected by two synapses to confirm signal transmission. The proposed circuit was fabricated using a 0.5μm double-poly-CMOS (complementary metal-oxide semiconductor) technology. Measurements of the fabricated single neuron and three-neuron chain were carried out by applying an input stimulus in condition of 5V DC power supply, and the results were compared to the simulations.

Smart sensor interfacing circuit using square-rooting current-to-frequency conversion

A universal sensor interfacing circuit is presented in this paper. It is capable of giving a digital output directly proportional to various types of measured quantities, where those measured quantities are proportional to the square root of some other type of quantity. This sensor interfacing circuit is a square-rooting current-to-frequency converter. The design is based on two current-controlled resistors in CMOS technology with bisection of the input voltage used in place of the ordinary resistors within the relaxation oscillator. There is no need for highly stable voltage or current references in the proposed design. The temperature stability of the design is achieved without the need for any specific setting of the process parameters. Experimental results, obtained on a circuit implemented by discrete components, confirm the predictions of the analysis performed. The relative errors are less than 1% for the input current range from 12 µA to 650 µA, and for the output frequency range from 231 Hz to 2.625 kHz. A solution for extending the input current dynamic range is also given in the paper.

New simple square-rooting circuits based on translinear current conveyors

Two new square-rooting circuits, based on second-generation current-controlled current conveyors (CCCIIs), are presented. The first square-rooting circuit consists of two CCCIIs, one current-controlled resistor and two grounded resistors. The input signal of the first circuit is a voltage, and output is the voltage proportional to the square root of input voltage. The second one consists of two CCCIIs and a current-controlled resistor. In the second circuit, the input signal is a current, and output is the current proportional to the square root of input current. Each circuit realizes by using a current-mode technique; hence the proposed square-rooting circuits are simple circuitry, wide dynamic range and wide bandwidth. The proposed square-rooting circuits were confirmed by using PSPICE simulation.

A SPICE-Oriented Method for Finding DC Operating Points of Nonlinear Circuits Containing Piecewise-Linear Macromodels

Recently, efficient algorithms have been proposed for finding all characteristic curves of one-port piecewise-linear (PWL) resistive circuits. Using these algorithms, a middle scale one-port circuit can be represented by a PWL resistor that is neither voltage nor current controlled. By modeling often used one-port subcircuits by such resistors (macromodels), large scale circuits can be analyzed efficiently. In this paper, an efficient method is proposed for finding DC operating points of nonlinear circuits containing such neither voltage nor current controlled resistors using the SPICE-oriented approach. The proposed method can be easily implemented on SPICE without programming.

A novel current limitation principle basedon application of liquid metals

In this paper, a new current limiting principle based on the application of liquid metals is proposed. This principle takes advantage of the arcless commutation of currents to a gradually increasing parallel resistance and makes it possible to realize a current-controlled resistor for very high currents, which can be used to limit the fault currents in power networks. The conditions for the arcless current commutation are investigated theoretically and the optimum profile for the parallel resistor is derived. An experimental setup is constructed to investigate the behavior of the separating contacts under different current amplitudes, different current steepnesses, and different resistance profiles. The experimental results relating to the commutation phase are compared to the theoretical limits

Linear differential-algebraic equations with properly stated leading term: Regular points

We consider in this work linear, time-varying differential-algebraic equations (DAEs) of the form A ( t ) ( D ( t ) x ( t ) ) ′ + B ( t ) x ( t ) = q ( t ) through a projector approach. Our analysis applies in particular to linear DAEs in standard form E ( t ) x ′ ( t ) + F ( t ) x ( t ) = q ( t ) . Under mild smoothness assumptions, we introduce local regularity and index notions, showing that they hold uniformly in intervals and are independent of projectors. Several algebraic and geometric properties supporting these notions are addressed. This framework is aimed at supporting a complementary analysis of so-called critical points, where the assumptions for regularity fail. Our results are applied here to the analysis of a linear time-varying analogue of Chua's circuit with current-controlled resistors, displaying a rich variety of indices depending on the characteristics of resistive and reactive devices.

Finding All DC Operating Points of Piecewise-Linear Circuits Containing Neither Voltage nor Current Controlled Resistors

Recently, efficient algorithms have been proposed for finding all characteristic curves of one-port piecewise-linear resistive circuits. Using these algorithms, a middle scale one-port circuit can be represented by a piecewise-linear resistor that is neither voltage nor current controlled. In this letter, an efficient algorithm is proposed for finding all dc operating points of piecewise-linear circuits containing such neither voltage nor current controlled resistors.

A square-rooting current-to-frequency converter

A square-rooting current-to-frequency converter is presented in this paper. It has been designed by using one relaxation oscillator where a current-controlled resistor in CMOS technology with bisection of the input voltage is used instead of the ordinary resistor. In this way, the time constant of the relaxation oscillator is current-controlled. There is no need for a high stable voltage or current references in the proposed circuit. By appropriate setting of the process parameters of the MOSFETs used, the temperature variations of the output frequency can be made smaller than 7.6/spl times/10/sup -3/%/K. Experimental results confirm that the behavior of the proposed square-rooting CFC is in good agreement with the predictions of the analysis performed. According to these results, relative errors are less than 1% for the input current range from 35 /spl mu/A to 15 mA, and for the output frequency range from 1.45 kHz to 9.80 kHz.

Electrical simulation of a p–i–n image sensor

We have modelled a p–i–n image sensor under local illumination through a two-dimensional non-linear circuit. The sensor is described as an array of photodiodes interconnected through lateral resistors, which model the sheet resistance of the doped layers. Under small-signal analysis, each photodiode is modelled by a current-controlled resistor proportional to the inverse of the photocurrent. A SPICE based simulator is used to analyse the sensor output characteristics. Several configurations and contact geometries are analysed for the image transducer. The image responsivity, the spatial resolution and the image distortion are modelled by changing the ratio between the transversal and the lateral resistors or the acquisition points. Results show that the geometry and location of the contacts affect the distortion of the restored image. The conductivity of the doped layers and the light flux illumination influences the image resolution and accuracy. The simulated and experimental results were found in a good agreement.

Low-voltage relaxation oscillator

A relaxation oscillator employing an S-shaped current-controlled nonlinear resistor composed of two bipolar transistors and a single resistor is proposed. The oscillator produces a unipolar sawtooth waveform and is suitable for low-voltage applications.

Class AB current-controlled resistor for high performance current-mode applications

A class AB current-controlled grounded resistor based on a translinear loop implemented from bipolar transistors is described. Simulation results show that its value is tunable from 30 to ~100 kΩ with frequency responses up to 100 MHz and beyond. With 12.5 V supply voltages, the total harmonic distortion (THD) is <1% for peak to peak magnitudes of the input current >2.5 times the value of the control current. To illustrate its suitability, the results of a controlled amplifier, using this resistor and operating in current-mode, are also given.

Nonlinear SPICE models for physiologic systems

Most biological systems are nonlinear but investigators interested in modeling them often make linear approximations to avoid performing tedious manual calculations. SPICE (Simulation Program with Integrated Circuit Emphasis, developed at the University of California, Berkeley, CA), an electrical circuit simulation program, is frequently used for creating and analyzing linear network models of physiologic and pathophysiologic processes. However, few investigators use the full capabilities of the program by modeling nonlinear elements. We developed six nonlinear SPICE elements, allowing simplified modeling of most commonly encountered physiologic processes. These are provided as subcircuits that can be easily incorporated into existing SPICE models. Included are voltage and current controlled nonlinear resistors, capacitors and inductors. In addition, we describe adders, multipliers, powers, inverse, and derivative functions.

Van der Pol and chaos

Experimental confirmation has been made on a driven relaxation oscillator circuit, first presented by Van der Pol, of the periodadding route to chaos. The nonlinear element in the circuit is a neon bulb, modeled by a three-segment piecewise-linear current-controlled resistor. A simple nonlinear circuit model has been used to reproduce in simulations the experimentally-observed period-adding phenomenon.

Design of General Voltage- or Current-Controlled Resistive Elements and their Applications to the Synthesis of Nonlinear Networks

New structures are proposed for the realization of voltage- or current-controlled resistors and conductors. The new devices have improved sensitivity parameters if compared with previously reported modules. Also an original contribution is the design of ungrounded elements which enlarge the usefulness of these structures. Applications of these elements to the synthesis of resistive nonlinear networks are studied. Experimental realizations are given and are in agreement with the theoretid results.