Variation Of Current Gain Research Articles

Analysis of Quantum-well Heterojunction Emitter Bipolar Transistor Design

The paper presents the analysis of Quantum-well Heterojunction Emitted Bipolar Transistor Design based on physical parameters with numerical computations. The specific objective of this work is to enhance the physical performance of the Quantum-well Heterojunction Emitted Bipolar Transistor Design in real world applications. There have been considered on the III-V compound materials like GaAs for p-type layer, AlGaAs for n-type layer and InGaAs for quantum-well layer for different kinds of junctions which were developed in HEBT structure. In this analyses, the parameters for implemented HEBT structure were evaluated to find the multi-quantum-well band diagram, operating frequency (unity beta frequency), rise time, storage delay time, fall time, minority carrier distribution, current gain variation, voltage-current characteristics and phonon control on quantum-well device. In these analyses, the physical parameters were carried out based on the experimental studies from the recent research works and many literatures. The physical parameters which used in this HEBT structure have been provided to solve the real fabrication problems by using theoretical concepts. The quantum-well device based on III-V compound materials was performed by using numerical techniques with the help of MATLAB. The simulation results confirm that the developed HEBT structure was suitable for fabricating the real devices for high performance applications.

Lower-power, high-linearity class-AB current-mode programmable gain amplifier

A novel class-AB implementation of a current-mode programmable gain amplifier (CPGA) including a current-mode DC offset cancellation loop is presented. The proposed CPGA is based on a current amplifier and provides a current gain in a range of 40 dB with a 1 dB step. The CPGA is characterized by a wide range of current gain variation, a lower power dissipation, and a small chip size. The proposed circuit is fabricated using a 0.18 μm CMOS technology. The CPGA draws a current of less than 2.52 mA from a 1.8 V supply while occupying an active area of 0.099 μm2. The measured results show an overall gain variation from 10 to 50 dB with a gain error of less than 0.40 dB. The OP1dB varies from 11.80 to 13.71 dBm, and the 3 dB bandwidth varies from 22.2 to 34.7 MHz over the whole gain range.

Effect of bias condition on heavy ion radiation in bipolar junction transistors

The characteristic degradations in a silicon NPN bipolar junction transistor (BJT) of 3DG142 type are examined under irradiation with 40-MeV chlorine (Cl) ions under forward, grounded, and reverse bias conditions, respectively. Different electrical parameters are in-situ measured during the exposure under each bias condition. From the experimental data, a larger variation of base current (IB) is observed after irradiation at a given value of base-emitter voltage (VBE), while the collector current is slightly affected by irradiation at a given VBE. The gain degradation is affected mostly by the behaviour of the base current. From the experimental data, the variation of current gain in the case of forward bias is much smaller than that in the other conditions. Moreover, for 3DG142 BJT, the current gain degradation in the case of reverse bias is more severe than that in the grounded case at low fluence, while at high fluence, the gain degradation in the reverse bias case becomes smaller than that in the grounded case.

A balanced output CMOS OTA with wide linear current tunable range

A new CMOS-based balanced output operational transconductance amplifier (BOTA) with very wide linear current tunable range is proposed in this paper. The design technique is achieved by the combination of a fully differential transconductor and an electronically variable current gain stage. The transconductance gain of the proposed BOTA can be linearly tuned by an external bias current for more than 4 decades, with less than 4% nonlinearity for the linear input-voltage range of about 0.2 V peak. The OTA is designed in 0.5 μm AMIS technology. The performance of the proposed circuit is discussed and confirmed through application example and PSPICE simulation results.

FULLY PROGRAMMABLE UNIVERSAL FILTER WITH INDEPENDENT GAIN-ω0-Q CONTROL BASED ON NEW DIGITALLY PROGRAMMABLE CMOS CCII

A fully programmable second-order universal filter with independently controllable characteristics is presented in this paper. The proposed filter is based on a new ± 0.75 V second-generation current conveyor with digitally programmable current gain. The input stage of the current conveyor is realized using two complementary MOS differential pairs to ensure rail-to-rail operation. The output stage consists of a Class-AB CMOS push-pull network, which guarantees high current driving capability with a 47.2 μA standby current. The digital programmability of the current conveyor, based on transistor arrays and MOS switches, provides variable current gain using a digital code-word. Two approaches for implementing current conveyors with programmable current gain either greater or less than one are described. The fully programmable universal filter and the proposed digitally programmable current conveyor circuits are simulated using PSPICE with 0.25 μm CMOS technology from MOSIS.

Precision Temperature Measurement Using CMOS Substrate PNP Transistors

This paper analyzes the nonidealities of temperature sensors based on substrate pnp transistors and shows how their influence can be minimized. It focuses on temperature measurement using the difference between the base-emitter voltages of a transistor operated at two current densities. This difference is proportional to absolute temperature (PTAT). The effects of series resistance, current-gain variation, high-level injection, and the Early effect on the accuracy of this PTAT voltage are discussed. The results of measurements made on substrate pnp transistors in a standard 0.5-/spl mu/m CMOS process are presented to illustrate the effects of these nonidealities. It is shown that the modeling of the PTAT voltage can be improved by taking the temperature dependency of the effective emission coefficient into account using the reverse Early effect. With this refinement, the temperature can be extracted from the measurement data with an absolute accuracy of /spl plusmn/0.1/spl deg/C in the range of -50 to 130/spl deg/C.

Elimination of burn-in effect in carbon-doped InGaP/GaAs HBTs by hydrogen lateral diffusion

Hydrogen lateral diffusion by annealing at low temperature was proposed to eliminate the burn-in effect in carbon-doped InGaP/GaAs heterojunction bipolar transistors (HBTs). After a thermal annealing at 480 °C for 30 min, the current gain variations caused by the electrical stress decreased from 42.7% to 2.6% as the emitter width was reduced from 100 to 5 μm. After the annealing process, the sheet resistance was decreased from 194.4 to 162.7 ohm/sq. as the van der Pauw line widths was reduced from 65 to 5 μm. Effective doping concentration in base layer was increased by removal of incorporated hydrogen atoms. Degradation of device characteristics was not obvious after annealing by comparing the ratio difference of current gain to base sheet resistance.

Investigation of short-term current gain stability of GaInP/GaAs-HBTs grown by MOVPE

Initial current gain variation in GaInP/GaAs-HBTs stressed at high-current density was investigated in dependence on base–dopant concentration and hydrogen passivation. It is shown that current-induced acceptor activation results in short-term current gain reduction, but does not affect emitter–base heterojunction properties. The incorporation of hydrogen during growth and the resulting passivation of carbon acceptors in the base layer depends mainly on carbon doping level and the precursors present during growth and cool-down. Under the growth conditions used, in-diffusion of hydrogen within AsH 3-rich growth steps turned out to be the major source of base–dopant passivation. Utilizing the blocking effect of n-type layers for H + in-diffusion we were able to reduce the base passivation ratio [H]/[C] to 0.1 leading to significant improvements in gain stability. It is shown that current gain instabilities can be completely suppressed by using a high-current density pre-stress treatment.

Optimization of a 0.6 μm, single polysilicon emitter bipolar technology versus narrow emitter effects

A novel 0.6μm, single polysilicon emitter bipolar technology has been optimized in order to reduce the consequences of narrow emitter effects (NEE) appearing at the laterals of the emitter area. The primary technological mechanisms of these effects have been studied and differentiated for this technology. They have been found to be the polysilicon over-etch into the underlying silicon, the pedestal oxidation, both of them in the area of the extrinsic base implantation, and the extrinsic base lateral diffusion. Designs of experiments techniques have been used in order to study all these technological elements and their effect on the final performance of the transistors. Common emitter current gain variation versus emitter width has been studied by means of test structures and an optimization method is proposed. Lateral diffusion of extrinsic base has been identified as main source of NEE in this technology, which reduces the transistors current gain. Pedestal oxidation has been identified as secondary source of these effects, acting in an opposite way of lateral diffusion increasing the transistors current gain. This opposed effects have been tuned in the technological optimization to minimize the NEE by means of a mutual compensation.

Reliability investigation of implanted microwave InGaP/GaAs HBTs

In this paper, we report the fabrication and characterisation of C-doped InGaP/GaAs microwave HBTs using a planar self-aligned technology based on O +/H + or O +/He + implant isolation schemes. We observed current gain variations with emitter/base geometries in the H + implanted HBTs while no such variation was observed in the He + implanted transistors. This latter phenomenon is characterised by a current gain increase in the smaller device and this was attributed to a decrease of the hole concentration in the base, caused by the formation of CH complexes in the C-doped GaAs base region. We therefore recommend the use of O +/He + implant scheme for the fabrication of reliable high performance C-doped base HBTs.

An Electronically Tunable Sinusoidal Oscillator Suitable for High Frequencies Operation Based on a Single Dual-Output Variable-Gain CCII

A novel sinusoidal oscillator, constructed from only one CCII with variable current gain, is presented and analyzed. The oscillator provides electronically tunable frequency, with good stability and low sensitivities, while variation of current gain does not affect the condition of oscillations. By the proposed circuit topology, the parasitic elements which exist at current conveyor terminals are absorbed by the external components and their action is diminished. Moreover, the parasitic poles of the current conveyor are taken into account and compensation technique and design criteria are applied, so that the oscillator can operate above 35 MHz.

Space-charge recombination currents and their influence on the dc current gain of AlGaAs/GaAs Pnp heterojunction bipolar transistors

The effects of Shockley–Read–Hall, Auger, radiative, and intrinsic surface base recombination processes in the emitter-base space-charge region on the current gain of Pnp AlGaAs/GaAs heterojunction bipolar transistors are analyzed. At low forward emitter-base bias, the current gain of a typical Pnp AlGaAs/GaAs heterojunction bipolar transistor is shown to be reduced substantially below its value calculated while neglecting recombination currents in the emitter-base space-charge region. Excellent agreement between theory and experiment is found for the current gain variation versus collector current density for a Pnp device recently reported by Slater et al. [IEEE Electron Device Lett. 15, 91 (1994)].

The effect of base-emitter space-charge recombination on the temperature dependence of current gains in InGaP/GaAs and AlGaAs/GaAs HBTs

In this study, various N-p-n heterojunction bipolar transistors (HBT) structures with high C-doped bases, grown by metal-organic chemical vapour deposition (MOCVD), have been fabricated with identical geometry and processing steps. Measured results show that in addition to the intrinsic heterojunction emitter injection efficiency, the base bulk recombination plays an important role in maintaining the current gain at high temperature. Furthermore, it is shown that emitter/base space-charge region recombination has a significant detrimental effect on the variation of current gain with increasing temperature. A theoretical model is presented which predicts well the current gain variation with temperature for both AlGaAs/GaAs and InGaP/GaAs HBTs.

Noninteracting electronically tunable CCII-based current-mode biquadratic filters

A complete state variable biquadratic filter built by CCIIs with variable current gain is presented and analysed. All the coefficients of the filter can be independently tuned through the variable current gain factors of the current conveyors. The authors propose fundamental techniques for the circuit implementation of the filter from the state variable block diagram. Design criteria to minimise the influence of the current conveyors' parasitic elements on the filter performance are presented. Based on the principles upon which the general biquadratic filter was constructed, a universal filter is proposed which implements the low-pass, high-pass, band-pass, band-reject and all-pass second order transfer functions simultaneously. Experimental measurements using Senani's current conveyor as well as PSPICE simulation using Surakampontorn's CCII were very close to theoretical values.

Gate-controlled lateral PNP BJT: characteristics, modeling and circuit applications

This paper describes the electrical characteristics, modeling and some circuit applications of a gate-controlled lateral pnp transistor (GC-LPNP) which has four electrodes-collector (C), base (B), emitter (E) and gate (G), and was fabricated using a 0.8 /spl mu/m BiCMOS technology. This device is composed of a surface PMOS FET and a bulk lateral pnp BJT in parallel, and it has unique dc characteristics of either variable current gain /spl beta//sub F/ of 10/sup 2//spl sim/10/sup 4/ for V/sub G/ variations from 0.4 to -0.4 V at V/sub E/ biases of 0.4 to 0.6 V, or variable transconductance g/sub M/ that increases by 3/spl sim/10 times as V/sub E/ increases from 0.4 to 0.7 V at V/sub G/ biases of -0.2 to -0.4 V. A circuit model of this new device, which is suitable for SPICE circuit simulation is proposed, and this model gives good agreement to the measured current-voltage curves over a wide range of V/sub C/-, V/sub E/- and V/sub G/-variations. Using this new four-electrode hybrid device, some special functional analog circuits, such as a variable-gain amplifier (VGA) and a mixer circuit, can be built very easily and exhibit good performance, For the VGA circuit, variations of the ac gain control of 0.4/spl sim/5.5 times for /spl delta/V/sub G/ varies over 1 V was obtained; and for the mixer, a conversion gain of 5 dB to 12 dB for input RF signal up to 400 MHz was obtained. PSPICE simulation results for the VGA circuit using the GC-LPNP device model are in good agreement with measurements. Finally, this new device which was fabricated using a typical BiCMOS technology, can be directly integrated with other digital/analog VLSI circuits for very attractive system applications, such as portable wireless communication systems.

Unique dc characteristics of a new gated lateral pnp bipolar junction transistor (BJT) using 0.8 μm BiCMOS technology

In this paper, the detailed device dc performance of a gated lateral pnp (LPNP) device that has five terminals, collector C, base B, emitter E, gate G, and substrate S, and is fabricated in a 0.8 μm BiCMOS technology is described. Because this gated LPNP has two inputs and one output, it shows unique dc characteristics of variable current gain, βF, of 102 ~ 104 with VG variations of 0.4 to – 0.4 V; variable transconductance, gM, which increases 3 ~ 10 times as VE increases from 0.4 to 0.7 V. Based on these unique features, this new device is attractive for some analog circuit applications; for example, when used as a mixer, it has a conversion gain of 5–12 dB for an input RF signal up to 400 MHz.

Finite element analysis of SiGe heterojunction devices

Two SiGe devices, a n/sup +/-n-p heterojunction diode and an n-p-n HBT have been analyzed using a two-dimensional bipolar device simulator which is based on the finite element method. The various shape functions used in the finite element formulations have been detailed. The dependence of the device characteristics on the various Ge mole-fraction material parameters has been studied. The variation of current gain of SiGe HBT with temperature is discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Programmable Second-Generation Current-Conveyor With Variable Current Gain

A new programmable second-generation current-conveyor is proposed. The proposed circuit uses a commercially available second-generation current-conveyor and one operational transconductance amplifier. Simulation results confirming the presented theory are included.

Study of proton radiation effects on analog IC designed for high energy physics in a BiCMOS-JFET radhard SOI technology

We present experimental results from a fast charge amplifier and a wideband analog buffer processed in the DMILL BiCMOS-JFET radhard SOI technology and irradiated up to 4.5/spl times/10/sup 14/ protons/cm/sup 2/. In parallel, we have irradiated elementary transistors. These components were biased and electrical measurements were done 30 min after beam stop. By evaluating variations of main SPICE parameters, i.e., threshold voltage shift for CMOS and current gain variation for bipolar transistors, we have simulated the wideband analog buffer at different doses. These SPICE simulations are in good agreement with measured circuit degradations. The behavior of the charge amplifier is consistent with extraction of transconductance and pinch-off voltage shift of the PJFET. >

On the modelling of poly silicon emitter transistors

Abstract The variations of base and collector current with base-emitter voltage of polysilicon emitter transistors are studied. A model is suggested which incorporates transport through the monosilicon and polysilicon layers as well as tunnelling through the interfacial oxide layer. The voltage dependence of band bending Ψs and the probability of tunnelling P h are also considered in the model, which is capable of predicting the nonlinear I B−V BE characteristics, the variation of base current with polysilicon layer thickness, and the variation of current gain with temperature, as observed in practice. Results predicted by the model are in good agreement with published data.