“GAMBIT: GAte Modulated BIpolar Transistor”

A planar, interdigitated, integrated device structure is described whose characteristics show a voltage controlled negative resistance between two of its terminals. This negative resistance can be controlled by the applied bias to a third terminal. Devices have been fabricated with this structure to achieve negative resistance values ranging from a few hundred thousand ohms down to less than a hundred ohms. The physical mechanisms that give rise to this negative resistance are described and a dc analysis of its behavior is presented. The analysis shows excellent agreement with the observed device characteristics.     

A First-Order Markov Model for Understanding Delta Modulation Noise Spectra

A first-order Markov process is used to model the sequence of quantization noise samples in delta modulation. An autocorrelation parameterCin the Markov model controls the shape of the noise spectrum, and asCdecreases from 1 to 0 and then to -1, the spectrum changes from a low-pass to a flat, and then to a high-pass characteristic. One can also use the Markov model to predict the so-called out-of-band noise rejection that is obtained when delta modulation is performed with an oversampled input, and the resulting quantization noise is lowpass filtered to the input band. The noise rejectionGis a function ofCas well as an oversampling factorFand an interesting asymptotic result is thatG=frac{1-C}{1+C} dot FifF gg frac{1+C}{1-C} dot frac{pi}{2}. Delta modulation literature has noted the importance of the specialGvalues,Fand2F. These correspond to autocorrelation values of 0 and -1/3.     

On the Delta Modulation of a First-Order Gauss-Markov Signal

Consider the delta-modulation (DM) of a first-order Gauss-Markov signalX. Let the adjacent-sample correlation inXbec, and let the (first-order) DM predictor coefficient bea. We express the quantizer input Qrin the form[S_{r} - aE_{r - 1} + (c - a)X_{r - 1}], where Sris an "innovations" term,aE_{r - 1}denotes the effect of quantizationerror(E)feedback and(c - a)X_{r - 1}reflects the effect of using ana neq c. For the important case ofc rightarrow 1(which models over-sampled DM inputs), we propose the simplifying assumption [7] of uncorrelatedXandE; with this assumption, our formalization of quantizer input leads very simply to interesting results in linear (LDM) and adaptive delta modulation (ADM). The LDM results are generalizations of known expressions for optimum values ofa, and the step-size Δ, and the value of signal-to-noise ratio SNR. For ADM, we derive optimum multiplier values for step-size adaptations with a one-bit memory, using the case ofc sim a = 1for simplicity. Our results depend on modeling instantaneous step-size adaptation as a mechanism for tracking the expected magnitude ofQ; existing literature has formalized such adaptation models only for the case of multi-bit quantizers.     

Analytical solutions for the breakdown voltage of abrupt cylindrical and spherical junctions

Analytical solutions for the breakdown voltage of abrupt cylindrical and spherical junctions have been obtained, using suitable approximations for the electric field in the depletion layer. These solutions are shown to be within ±1% of exact computer solutions for doping densities of less thant 10¹⁶ cm^?1. By normalization to the parallel plane case, these solutions have been presented in a form which allows the computation of the breakdown voltage of both cylindrical and spherical junctions using a single curve for each situation.     

Lateral n-channel inversion mode 4H-SiC MOSFETs

Advances in MOS devices on silicon carbide (SiC) have been greatly hampered by the low inversion layer mobilities. In this paper, the electrical characteristics of lateral n-channel MOSFETs fabricated on 4H-SiC are reported for the first time. Inversion layer electron mobilities of 165 cm²/V·s in 4H-SiC MOSFETs were measured at room temperature. These MOSFETs were fabricated using a low temperature deposited oxide, with subsequent oxidation anneal, as the gate dielectric