N.Sen Gupta

Bio: N.Sen Gupta is an academic researcher from University of Calcutta. The author has contributed to research in topics: Transistor & Common emitter. The author has an hindex of 1, co-authored 1 publications receiving 9 citations.

On the variation of cut-off frequency with emitter end concentration of a diffused base transistor

Abstract: The effect of mobility degradation at high impurity concentrations on the cut-off frequency of a diffused base transistor with exponential impurity profile in the base has been considered analytically. It has been shown that the cut-off frequency exhibits a maximum with increase in emitter and concentration. The results are compared with those of complementary error function and Gaussian base impurity profiles.

Effect of back surface field on photocurrent in a semiconductor junction

Abstract: An analysis has been carried out for a silicon diffused junction having a back surface field, with particular reference to the generation of photocurrent. The minority carrier distribution, and, photocurrent, as a function of width of the base region of this device, has been calculated. It has been observed that for a back surface field silicon diffused junction, the photocurrent reaches its maximum value at a much shorter width of the base layer. The dependence of photocurrent on the base layer impurity concentration has been studied after taking into account the dependence of diffusion length and diffusion constant on the impurity concentration in the base layer. The photocurrent for the same structure having a drift field in the base layer and a low high junction at the back has also been calculated, and the results indicate that the effect of a high-low junction on photocurrent in this case is less pronounced. A qualitative description of the photoeffect in pp + junction has also been included and the importance of including photovoltaic effect at the low-high junction to explain the overall performance of device has been stressed.

Analytical relations for the base transit time and collector current in BJTs and HBTs

Abstract: A simple analytical model for a base with an exponential doping profile is presented. The proposed approach improves previous work in that it accounts for all significant effects, namely the dependence of the mobility on doping concentration and electric field, heavy-doping effects, and finite carrier velocity at the collector edge. The model also applies to HBTs with a linearly graded composition. The model results show that the dependence of the mobility on the electric field has a significant impact on device performance, strongly limiting the beneficial effect of the built-in field on the minority-carrier current and transit time.

An approximate model for the graded-base transistor

Abstract: The graded-base region of a conventional diffused-base transistor can be approximately modeled as two uniformly-doped regions, one heavily-doped near the surface and the other lightly-doped. This fundamental idea, combined with the Fletcher boundary conditions and the ambipolar approach, yields a one-dimensional analytical model for the graded-base transistor. For downward operation, this model—called the n+pp−n+ transistor model—has only slight advantages as compared with existing analytical models such as the conventional uniform-base transistor model. For upward operation, the n+pp−n+ transitor model has significant advantages.