Unijunction Research Articles

Analog realization of arbitrary one-dimensional maps

An increasing number of applications of a one-dimensional (1-D) map as an information processing element are found in the literature on artificial neural networks, image processing systems, and secure communication systems. In search of an efficient hardware implementation of a 1-D map, we discovered that the bifurcating neuron (BN), which was introduced elsewhere as a mathematical model of a biological neuron under the influence of an external sinusoidal signal, could provide a compact solution. The original work on the BN indicated that its firing time sequence, when it was subject to a sinusoidal driving signal, was related to the sine-circle map, suggesting that the BN can compute the sine-circle map. Despite its rich array of dynamical properties, the mathematical description of the BN is simple enough to lend itself to a compact circuit implementation. In this paper, we generalize the original work and show that the computational power of the BN can be extended to compute an arbitrary 1-D map. Also, we describe two possible circuit models of the BN: the programmable unijunction transistor oscillator neuron, which was introduced in the original work as a circuit model of the BN, and the integrated-circuit relaxation oscillator neuron (IRON), which was developed for more precise modeling of the BN. To demonstrate the computational power of the BN, we use the IRON to generate the bifurcation diagrams of the sine-circle map, the logistic map, as well as the tent map, and then compare them with exact numerical versions. The programming of the BN to compute an arbitrary map can be done simply by changing the waveform of the driving signal, which is given to the BN externally; this feature makes the circuit models of the BN especially useful in the circuit implementation of a network of 1-D maps.

Silicon strain sensitive unijunction transistor with controlling p–n-junction

Abstract Theoretical studies of a silicon integral pressure transducer characteristics are made. The sensitive element of the transducer is a strain sensitive controlled unijunction transistor (SSCUJT) with controlling p–n-junction. The transistor has horizontal structure and could be considered as combination of p–n–p bipolar and n + –p–n + unijunction transistors. The unijunction transistor is integrated in the planar side of the silicon square-shaped diaphragm with two rigid islands (the EE-type diaphragm). Using Green’s function formalism characteristics of the pressure transducer are investigated and the optimal topology of the sensitive element is determined. It has been shown that high sensitive pressure sensors with frequency output could be created on base of the unijunction transistors.

A silicon stress-sensitive unijunction transistor

The performance of a silicon stress-sensitive unijunction transistor is investigated. The transistor is classed as a stress-sensitive semiconductor lateral bipolar device with an S-type input (emitter) I-V characteristic. The optimal layout of the device and its basic parameters are determined. The device can serve as a basis for designing relaxation oscillators with the physically integrated function of mechanical stress-to-signal frequency conversion at the output.

Optical Co-Incidence Gate

The paper explains Optical co-incidence gate, realized using Unijunction transistors (UJT), Light emitting diodes (LED) and Photo-resistors (LDR), which works on 1.8Vdc instead of 3Vdc. The power dissipation of the designed gate is only 3 mW. This optical gate finds application in the field of Mechatronics, Instrumentation and Fiber optics systems where intrinsic safety is of prime importance rather than speed of operation. Key words: Bistability, Intrinsic safety, and Low speed. (Af. J. of Science and Technology: 2002 3(2): 114-117)

ON RATIONAL PHASE-LOCKING OSCILLATIONS OF A SIMPLE SAWTOOTH OSCILLATOR WITH UJT

There are some reports about sawtooth oscillations on various systems. The authors constructed the sawtooth oscillator circuit exploiting a Uni-Junction Transistor (UJT), and investigated various nonautonomous-like oscillations induced by an external sinusoidal input. Different from the cases of ordinary differential equation (ODE) systems driven with some periodic oscillation, this input periodically alternates only the threshold of the mode transition. Many systems in various fields of electrical circuits, biology and so on utilize threshold variation or modulation between operational modes, and our system is a very simple representative. Though our circuit behaves as a piecewise-continuous ODE system, we will suggest one-dimensional map depending on the phase of the external sinusoidal input. And we will study the background about the existence of various rational locking mode in the analytic method, numerical investigations and circuit experiments, identifying our system as a discrete dynamical system. This paper reveals not only the existing regions of the respective modes, but also reports about respective itineraries of periodic solutions geometrically. Readers will see that the mode distribution constitutes a Cantor set structure.

Modelling and characterisation of the input I– V curves of bipolar JFET structures showing a negative resistance behaviour

An analytical model of the I– V input curves of normally on JFET structures for an arbitrary drain voltage is proposed. The model is capable to predict the occurrence of a negative resistance in the curves in agreement with numerical simulations and experiments. It is shown that, similarly to the unijunction transistor, the negative resistance is determined by the variation of the ohmic drain voltage occurring in the base as the gate voltage reaches the onset value of the conductivity modulation regime. Moreover the model can be considered the basic theory of the experimental method proposed [Solid-State Electron 43(7) (1999) 1201] for measuring the series resistance of lateral diodes.

Adaptive-learning neuron integrated circuits using metal-ferroelectric (SrBi/sub 2/Ta/sub 2/O/sub 9/)-semiconductor (MFS) FET's

An adaptive-learning neuron circuit was fabricated for the first time by integrating a metal-ferroelectric-semiconductor (MFS) FET and a complementary unijunction transistor (CUJT) on a silicon-on-insulator (SOI) structure. SrBi/sub 2/Ta/sub 2/O/sub 9/ (SBT) was selected as a ferroelectric gate material and it was deposited by liquid source misted chemical deposition (LSMCD) method. In fabrication of the circuit, a new selective etchant, NH/sub 4/F:HCl, was used to remove the unnecessary SBT film, since it was found from preliminary experiments that the parasitic ferroelectric capacitors prevented normal operation of the circuit. It was found that the drain current of the MFSFET was changed gradually by applying a number of input pulses with a sufficiently short duration time of 20 ns. The gradual change in the output pulse frequency of the neuron circuit was also demonstrated as the number of input pulses was increased.

Electrical Characteristics of Neuron Oscillation Circuits Composed of MOSFETs and Complementary Unijunction Transistors

A pulse frequency modulation (PFM) type neuron circuit composed of a metal-oxide-semiconductor field effect transistor (MOSFET) and a complementary unijunction transistor (CUJT) was fabricated on a silicon-on-insulator (SOI) structure as an approach to an adaptive learning neuron circuit using a metal-ferroelectric-semiconductor field effect transistor (MFSFET). The output pulse interval was controlled by changing the pulse duty ratio of input pulse signals as well as the magnitude of the DC input voltage. These results demonstrate that the electrical properties of MOSFET neuron circuits are good enough for future neural networks, that can be expected to be realized by replacing the MOSFET with an MFSFET. A new circuit using a complementary MOS (CMOS) Schmitt-trigger configuration is also proposed for improving output pulse amplitude.

Topography of low skin resistance points (LSRP) in rats.

Based on the electrical properties of the skin, a method employing the unijunction transistor (UJT) relaxation oscillator for detecting low skin resistance points (LSRP) was developed in this study. By means of this instrumentation, the topography of the LSRP in Wistar rats was developed. All the LSRP in the rats were found to be bilaterally and symmetrically distributed except those points located on the dorsal midline (i.e., governor vessel, GV) and the ventral midline (i.e., conception vessel, CV). The resistances of the LSRP on these two major vessels, including 14 CV points and 17 GV points of six rats were experimentally determined to be in the ranges of 179.4 +/- 41.2 K omega and 152.5 +/- 32.2 K omega, respectively. The resistances of the GV points were found in general to be lower than those of the CV points. Most non-LSRP, on the other hand, exhibited resistances of greater than 420 K omega. It is noted that the resistances of most LSRP increased yet still retained a separate identity within thirty minutes after the death of the animals, but the low resistance properties of some LSRP gradually disappeared thereafter and could not be detected by the relaxation oscillator.

Ferroelectric neuron circuits with adaptive-learning function

A neon circuit which consists of nonvolatile metal-ferroelectric-semiconductor field effect transistors (MFSFETs) and a uni-junction transistor (UJT) has been proposed. In the proposed circuit MFSFETs act as analog memories to store the synaptic weights which can be changed by the adaptive-learning process during the operations. In this paper, we first simulate the operation of the ferroelectric neuron circuit using a circuit simulator, SPICE. It is shown that the output frequency of the proposed neuron circuit can be changed after it processes a certain number of input pulses. Then, we report the fabrication of UJTs and UJT pulse oscillation circuits using silicon-on-insulator (SOI) substrates. It is found that the output frequency increases with decreasing the charging time of the capacitor in the circuit and that the operation at higher frequencies is possible for integrated UJT oscillation circuits. Finally, we demonstrate the memory and learning properties of n-channel ferroelectric-gate FETs using (Pb,La)(Zr,Ti)O 3 (PLZT) films. It is shown that the drain current of the PLZT/SrTiO 3/Si FETs can be controlled by a “write” pulse before the measurements.

Computer design and analysis of relaxation oscillator circuits applying unijunction transistors

Performance data for unijunction transistor devices and their applications as oscillator circuits operate at normal and elevated temperature levels (up to 140°C) as well as in nuclear radiation environments (up to 1000 Mrad) are presented either experimentally or theoretically. Different computer programs are suggested to solve the general equations for the relaxation oscillators' design and analysis and to introduce the operating conditions, temperature and nuclear radiation effects on their performance. It was found that the experimental and calculated data are in close agreement.

Studies of in vivo Gene Transfer by Electropulsation at the Low Skin Resistance Points (LSRPs)

Electropulsation has been proved to be a powerful technique for DNA transfection in vitro. This study was undertaken to assess the feasibility and evaluate the potential of applying this approach for facilitating gene transfer in vivo. The pCMVβ plasmid, containing the Escherichia coli lacZ open reading frame under the cytomegalovirus early promoter, was complexed with poly-L-lysine (PLL) and injected directly into the livers of Wistar rats; electropulsation was then applied either at the low skin resistance points (LSRPs) of the skin, the non-LSRP, or directly at the liver by either a portable electrostimulator or an electropulsation unit. The locations of the LSRPs were detected by the unijunction transistor (UJT) relaxation oscillator. Seventy-two hours after gene transfer, the animals were sacrificed and the livers were excised, followed by examination of the transgene expression. The results obtained from X-gal staining, in situ hybridization, and Western blot analysis indicated that lacZ gene was expressed in the livers. Variations of the electropulsation parameters, including site of electropulsation, wave type, amplitude of the pulses, repetition rate, duty cycle, and duration of electropulsation treatment, do not reveal any statistically significant effects of differences of these variables on the transgene expression. Comparison of the results obtained from direct injection of PLL/pCMVβ (1:1) followed by electropulsation at the LSRPs with that of direct PLL/pCMVβ (1:1) injection, however, suggests that gene transfer by electropulsation achieved a higher transfection efficiency in vivo (p >. 05).

Piecewise-linear modeling of I-V characteristics with SPICE

This paper presents a technique for piecewise-linear modeling of arbitrary nonlinear I-V characteristics with SPICE. In particular, I-V characteristics (including those exhibiting negative resistance) that lend themselves to piecewise-linear approximation are easily modeled using six elemental building blocks; three for voltage-controlled I-V characteristics and three for current-controlled I-V characteristics. The elemental building blocks are implemented with resistor, diode, independent voltage source, and independent current source SPICE primitives. Two of the elemental building blocks use the ability of SPICE to accept negative values for the resistance and diode saturation current parameters. The technique is applied to model a unijunction transistor and a tunnel diode. Two negative resistance oscillator examples which use these models are included; a current-controlled negative resistance sinusoidal oscillator (unijunction transistor) and a voltage-controlled negative resistance relaxation oscillator (tunnel diode). These examples have been used to teach the fundamentals of negative resistance oscillators and nonlinear effects to sophomores and juniors.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Adaptive-learning neuron circuits using ferroelectric thin films

Abstract Adaptive-learning neuron circuits are reviewed, in which a pulse frequency modulation (PFM) system is used and the interval of output pulses is changed through the learning process. Key devices of the circuits are MFSFETs (Metal Ferroelectric Semiconductor Field Effect Transistors). They are used for representing the synaptic weights of neurons and the polarity of the films is gradually changed by applying input pulses to the gates. In order to produce PFM signals, circuit using a UJT (unijunction transistor) is discussed. As a preliminary experiment for realization of MFSFETs, the electrical properties of metal ferroelectric metal (MFM) capacitor using sol-gel derived PZT films are discussed.

Pulsating neuron produced by electron-trapping materials

We report our results from the study of the dynamics of electron-trapping materials (ETM's) under simultaneous illumination of pulsed blue light and constant IR light. By combining the dynamic property of ETM with the S-shaped nonlinear I-V characteristic of a programmable unijunction transistor, we produce an optoelectronic pulsating neuron. A proof-of-concept experiment successfully produces oscillations and demonstrates the great potential of using ETM's to implement dense arrays of pulsating neurons.

Microprocessor Based Magnetic Fluxmeter using Unijunction Transistor Probe

A simple design of magnetic fluxmeter using 8085 microprocessor has been described. The circuit accurately measures the strength of magnetic field using the magnetic field dependent properties of a unijunction transistor. The transistor forms part of relaxation oscillator circuit whose frequency is affected by the presence of magnetic field. The magnetosensitivity of the proposed circuit is 40 counts Tesla−1. One of the salient features of the present design is that the microprocessor controls the ON-OFF action of electromagnet.

Experimental verification of periodic pulling in a nonlinear electronic oscillator.

An experimental investigation of entrainment and the phenomenon known as periodic pulling is described. Periodic pulling refers to the incomplete entrainment of an oscillatory nonlinear system by a periodically varying driving force. The process whereby the system's oscillation frequency is pulled toward the driving frequency stops short of complete synchronization and is interrupted at regular intervals. In this way, periodic pulling produces pulselike amplitude and frequency modulation in the system's oscillatory response. Associated with these combined, nonsinusoidal modulations is an asymmetric, or single-sided, spectral peak made up of spectral components at frequencies incommensurate with the undriven (spontaneous) and driving frequencies. The system being investigated uses a unijunction transistor as the nonlinear element in an electrical circuit. The behavior of the system is shown to resemble that predicted for a forced van der Pol oscillator with an adjustable nonlinear restoring force. For certain ranges of driving frequency and amplitude, when the system is not entrained to the driving force, periodic pulling is shown to alter the system's oscillatory response significantly from that expected for conventional amplitude modulation involving two sinusoids. The essential features of the periodic pulling phenomenon are observed and compared, with good agreement, to a model.

Measurement of static dielectric constants of supercritical fluid solvents and cosolvents: Carbon dioxide and argon, carbon dioxide, and methanol at 323 K and pressures to 25 MPa

A new apparatus for the measurement of dielectric constants of high pressure gases has been constructed. The apparatus consists of a recirculating visual flow cell and a concentric cylinder dielectric constant flow cell. Measurement of the dielectric constant is made by a unique counter-oscillator circuit, in which the capacitance is determined by relaxation of a unijunction transistor oscillator circuit and counted by a crystal oscillator. Dielectric constants are reported for supercritical mixtures of carbon dioxide + argon and carbon dioxide + methanol at a temperature of 322.9 K and pressures to 25 MPa. The dielectric constant shows a sharp increase near the critical pressure. Dielectric constants were linear with densities calculated by the Suzuki equation-of-state. The dielectric constant for the methanol-carbon dioxide system was found to be less than a mole fraction average of the pure component dielectric constants.

Brief communication. New static RAM cell based on the unijunction transistor

A new static RAM cell is proposed based on the negative resistance in the output V-I characteristic of a unijunction transistor.

An electronic integrating heat meter

The heat energy consumed by individual customers in a district heating system that uses hot water is found by integrating the flow rate (volume/second) and multiplying it by the temperature difference between the incoming and outgoing water. An electronic integrating heat meter is developed for this purpose using a programmable unijunction transistor (PUT) and linearized thermistor sensors. The temperatures of the incoming and outgoing radiator water are measured by means of the thermistor sensors mounted on the pipes connected to the radiator, and their temperature difference is converted to a current. The current is applied to a current-to-pulse frequency converter using the PUT that operates only during the time of the constant width of the pulses generated by a water-flow meter and correspond to the water-flow volume. Therefore, the number of counted output pulses of the current-to-pulse frequency converter shows the integrated multiplication of the flow rate and the temperature difference, which is the heat energy. The electronic circuit is simple and therefore not expensive. The accuracy of the heat meter is within +or-2% for a temperature difference up to 40 degrees C.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>