Tunnel Diode Amplifier SGEMP Response

The principle of super-regeneration can be applied to many electronic circuits to achieve large amplifications The advent of the tunnel diode has made available a device which, by virtue of its voltage controlled negative conductance region, can be used as the active element in a simple super-regenerative amplifier. In a tunnel diode super-regenerative amplifier the quenching process, necessary to start and interrupt the oscillations periodically, is simply accomplished by moving the operating point in the current-voltage characteristics from the negative conductance region to the positive conductance region The simplicity of the circuitry associated with the tunnel diode and its low noise capabilities make tunnel diodes super-regenerative amplifiers or detectors very attractive An analysis based on well-established super-regeneration theory shows that tunnel diodes can operate reliably in the super-regenerative mode. The results of the analysis compare with experimental results with good agreement The possibility of utilizing tunnel diode super-regenerative detectors or amplifiers in practical circuitry has boon demonstrated by their incorporation, with good performance, in actual communication circuits.

The effect of temperature change on stability of electrical characteristics of GaAs and GaSb tunnel diodes is studied. It is shown that thermal stresses developed at the boundary between the electrode alloy and the semiconductor lead to deformations (plastic and creep), localized mainly in the electrode layer. These deformations are sensed by the p-n junction which lies close to the phase boundary, which leads to a relaxation of peak current, and its hysteresis-type temperature dependence.

On the theory of hall-effect isolators for tunnel diode amplifiers

In this paper an attempt is made to present the work on microwave components/sub-assemblies that is being carried out at Himalayan Radio Propagation Unit, using microwave printed circuit techniques. The various microwave components/sub-assemblies designed and developed for the microwave communication system under development include the power divider, hybrid ring, directional couplers, balanced mixer and tunnel diode amplifier. The microwave printed circuits have the advantages of reduction in size and weight, better reliability and improved electrical performance over the conventional waveguide and coaxial microwave components.

AM to PM conversion in tunnel diode amplifiers

This paper reports on the modes of failure of GaSb tunnel diodes and a model which explains the major experimental observations. When GaSb tunnel diodes are biased at positive voltages well past the valley region, permanent changes in the tunnel diode characteristics occur. In this case both the peak and the valley currents go up with degradation. This is to be contrasted with GaAs tunnel diodes in which the peak current always goes down. When the GaSb tunnel diode is biased at a fixed voltage in the so-called "injection region," the peak and the valley currents increase exponentially with time with a well defined final value for each. The difference between the final and the initial values of the valley is larger than that of the peak. The peak current reaches its final value before the valley current. Under proper experimental circumstances it can be shown that the failure process not only continues after being initially biased in the "injection region" but is actually accelerated for a period of time by the removal of bias. The proposed model explains all the above observations and several others. It also explains how and why some reversible as well as irreversible changes are experimentally observed. Observed changes in capacitance with failure are consistent with the proposed model.

In this work we investigate experimentally and theoretically the performance of metamorphic/dislocated GaAs based tunnel diodes with dislocation densities (Nd) ranging from 2×105to 2×109cm−2. As it is commonly reported, we observe no performance degradation for Nd 109cm−2). However, interestingly we observe a noticeable improvement of peak current densities for diodes with moderate dislocation densities (∼20% at N=2.4×108 cm−2). Simulation of the tunnel diode characteristics, assuming a defect state assisted-tunneling/hoping, allows to partially account for this observation.

Approximate analyses published previously on tunnel-diode converters are basically phenomenological in nature by restricting the currents flowing through the tunnel diode or (and) the voltage across it to the signal, local oscillator, and intermediate frequencies only. Because of the nonlinear nature of the tunnel diode, many higher-order frequency components corresponding to harmonics and products, sums, and differences of the above mentioned frequencies are present. By including the effects of series resistance and series inductance and restricting the operating region within the parabolic portion of the tunnel-diode characteristics, the present analysis attempts to formulate the problem in a rigorous manner through the derivation of a second-order nonautonomous nonlinear differential equation with time-varying coefficients. The solution to a first-order approximation is obtained by incorporating a variational type treatment with an expansion type perturbation method. In an effort to verify the validity of the theoretical results obtained by the nonlinear analysis, an analog simulation is carried out since the control of required parameters in actual experiments is extremely difficult, especially in the microwave frequency region. The general agreement between the theoretical results and the analog simulation is promising and, therefore, should yield enough information to facilitate the control and adjustment of the various parameters in actual experiments especially in the microwave region. Specifically, we have verified by the analog simulation the theoretical prediction that the optimized conversion gain is obtained when the source resistance is about one third of the load resistance. In addition to minimizing the converter noise, the noise due to the first IF amplifier can also be minimized by selection of the correct converter load resistance by using Figs. 4 throngh 8.

The influences of interface roughness (IR) scattering on transmission coefficient and current-voltage ( I–V ) characteristics of double-barrier resonant tunneling diodes are investigated. Simulation results reveal that asymmetric interface roughness scattering on different interfaces of the heterostructure may result in asymmetric I–V characteristics. In addition, it is suggested that the splitting of subband energy levels inside the quantum well caused by IR with large terraces (≥15 nm) may be one of the causes leading to a steplike I–V curve in the negative differential resistance region.

This paper presents a fully analytical physics-based model for the current-voltage (I-V) characteristics of resonant tunneling diodes. We consider the whole electrical potential distribution in the structure, including the space charge regions in the emitter and collector layers. Additionally, we account for scattering mechanisms experienced by carriers during tunneling through the double barrier region as a function of the applied bias voltage. The model is validated with experimental and numerical data, yielding excellent agreement

This paper presents a theory for single-stage circulator-coupled negative resistance reflection amplifiers based on proposed realistic circuit models for frequency-dependent band-limited circulators and broadband negative resistance devices such as the tunnel diode. In particular, gain bandwidth limitations are derived which are imposed by both the inherent resonance associated with the nonreciprocal circulator junction and the reactive parasitic associated with the active device. These limitations are generally more restrictive than past results which assumed a "perfect" frequency-independent circulator and took into account only the device parasitic. In addition, a synthesis procedure is presented for realization of an absolutely stable amplifier with a prescribed nth-order Butterworth or Chebyscheff approximation to an ideally flat band-pass power gain characteristic. The approach employed is based upon the theory of reflection coefficient equalization between two reactively constrained resistances representing the pass band circulator and device immittance models. In addition, a band rejection out-of-band stabilizing network is absorbed in the pass band equalizer in accordance with an over-all synthesis procedure. Finally, the theory is verified by the construction and testing of an L-band tunnel diode amplifier having third-order maximally flat power gain centered at 1.46 Gc/s and with half-power bandwidths (430 Mcls and 355 Mc/s at 10 dB and 16dB midband gain) within six percent of those predicted by theory.

Impedance spectroscopy study of the retinal pigment epithelium: Application to the monitoring of blue light exposure effect on A2E-loaded in-vitro cell cultures

DC characteristics of resonant tunneling diodes (RTDs) and resonant tunneling high electron mobility transistors (RTHEMTs) are simulated utilizing a new methodology of parameter extraction for RTD. Good agreement between simulation results and measurements is achieved. Based on the simulations, a RTD-HEMT-RTD structure is proposed. It exhibits novel characteristics suitable for many kinds of applications, including early vision and multi-state memories.

Several techniques were proposed to achieve solid state spin filtering such as magnetic tunnel junctions comprised of half-metallic compounds or solid state Stern-Gerlach apparatus. Another alternative consists in using spin-dependent resonant tunneling through magnetically active quantum wells. Recent advances in molecular beam epitaxial growth made it possible to fabricate exotic heterostructures comprised of magnetic films or buried layers (ErAs, GaxMn1-xAs) integrated with conventional semiconductors (GaAs) and to explore quantum transport in these heterostructures. It is particularly interesting to study spin-dependent resonant tunneling in double-barrier resonant tunneling diodes (RTD) with magnetic elements such as GaAs/AlAs/ErAs/AlAs/ErAs/AlAs/GaAs, GaxMn1-xAs/AlAs/GaAs/AlAs/GaAs, and GaAs/AlAs/GaxMn1-xAs/AlAs/GaAs. We present the results of our theoretical studies and computer simulations of transmission coefficients and current-voltage characteristics of resonant tunneling diodes based on these double-barrier structures. Resonant tunneling of holes (GaxMn1-xAs-based RTDs) is considered. Our approach is based on k·p perturbation theory with exchange splitting effects taken into account. We analyze exchange splitting of different resonant channels as a function of magnetization as well as spin polarization of the transmitted current as a function of bias. We found that resonant tunneling I – V characteristics of the double-barrier magnetic hererostructures strongly depend on the doping level in the emitter as well as on the orientation of the magnetization.

contains documentations for the following functional modules used in the SCALE system: KENO-V which is an improved Monte Carlo criticality program; and JUNEBUG, a three-dimensional geometry plotting code.