Subthreshold analog/RF performance of underlap DG FETs with asymmetric source/drain extensions

DG FETs with underlap architectures exhibit better performance for logic applications owing to its improved immunity to short channel effects. In this work, we have analyzed the effect of symmetric and asymmetric source drain extensions in the underlap DG FETs for improved subthreshold analog and RF performance in the 45 nm gate length regime. The various figures of merits such as transconductance, transconductance generation factor and intrinsic gain along with cut-off frequency, maximum frequency of oscillation and gain–bandwidth product are investigated for symmetric and asymmetric drain extensions in the underlapped DG FETs. The underlap length of the asymmetric DG FETs is also varied for improved device performance parameters. For circuit analysis, a cascode amplifier is analyzed for higher gain by biasing the load transistor with the special importance in the subthreshold regime as CMOS circuits operated in this regime are very much attractive for ultralow-power high gain performances. For AC analysis, the gain–frequency curve of a common source amplifier is studied for the improved gain–bandwidth product and an improvement of about 55% was observed in the asymmetric DG underlap devices compared to its symmetric counterpart

Disseminated cutaneous histoplasmosis, an initial manifestation of hiv, diagnosed with fine needle aspiration cytology

Acute progressive disseminated histoplasmosis (PDH) may be the initial manifestation of human immunodeficiency virus (HIV). However, cutaneous involvement is very rare. We present an unusual case of acute PDH with multiple diffuse cutaneous papulonodular lesions predominantly on the face, trunk, and upper extremities, diagnosed initially with fine needle aspiration cytology (FNAC). Subsequent serological tests revealed positivity for antibodies for HIV 1 and 2. The cytomorphological features were further confirmed by biopsy and histochemical stains. FNAC is a rapid, cost-effective tool that may be utilized in the diagnosis of papulonodular forms of PDH and for initiating prompt therapy. We discuss the clinical features, clinical differentials, and treatment of the condition

A New Threshold Voltage and Drain Current Model for Lightly/Heavily Doped Surrounding Gate MOSFETs

In this paper, we have presented a surface potential based drain current and threshold voltage model for surrounding gate MOSFETs that is valid for all doping concentrations. The Newton Raphson iterative technique is implemented for calculation of the potential at the surface and center of the channel and the drain current is then computed. The relative error between the potential values obtained from model and TCAD is within 2%. The drain current based on first iteration is much more accurate than the full depletion approximation. In the final part of this work, the threshold voltage is modeled based on two dimensional Poisson’s equation and the variation with channel radius is explored. A good match with reference data is observed

Short-channel drain current model for asymmetric heavily / lightly doped DG MOSFETs

The paper presents a drain current model for double gate metal oxide semiconductor field effect transistors (DG MOSFETs) based on a new velocity saturation model that accounts for short-channel velocity saturation effect independently in the front and the back gate controlled channels under asymmetric front and back gate bias and oxide thickness. To determine the front and the back-channel velocity saturation, drain-induced barrier lowering is evaluated by effective gate voltages at the front and back gates obtained from surface potential at the threshold condition after considering symmetric and asymmetric front and back oxide thickness. The model also incorporates surface roughness scattering and ionized impurity scattering to estimate drain current for heavily / lightly doped channel for short-channel asymmetric DG MOSFET and a good agreement has been achieved with TCAD simulations, with a relative error of around 3–7%.Published versio