http://nopr.niscair.res.in/handle/123456789/11705 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/11718 Title: Low-frequency quadrature sinusoidal oscillators using current differencing buffered amplifiers <br/> <br/>Authors: Lahiri, Abhirup <br/> <br/>Abstract: This paper proposes new realizations of low-frequency quadrature sinusoidal oscillators using CDBA (current differencing buffered amplifier) as the active building block (ABB). The proposed circuits employ reduced number of components, namely two CDBAs, four (or five) resistors and two true/virtually grounded capacitors. The oscillators provide two quadrature voltage outputs and the condition of oscillation (CO) and the frequency of oscillation (FO) are independently controllable. Low frequency generation is enabled by the presence of difference term in the numerator of FO. The non-ideal analysis and sensitivity study of the circuits have been carried out and the circuits exhibit satisfactory sensitivity performance. SPICE simulation results are included that validate the working of the circuit. <br/> <br/>Page(s): 423-428 Sun, 29 May 2011 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/11717 Title: Effect of structural parameters on 2DEG density and C~V characteristics of Al_xGa_1−xN/AlN/GaN-based HEMT <br/> <br/>Authors: Lenka, T R; Panda, A K <br/> <br/>Abstract: A new High Electron Mobility Transistor (HEMT) model is proposed in this paper by introducing a thin AlN layer in nanoscale range into the conventional Al_0.3Ga_0.7N/GaN-based HEMT keeping the Al content of 30%. The AlN layer is very sensitive towards the development of polarization charges at the hetero interface and results into high 2DEG density (<i>n</i>_s). The role of AlN layer is essentially very much suitable in order to reduce various scattering exist at the hetero interface of the conventional GaN based devices. The change of various structural parameters such as Al mole fraction of Al_xGa_1−xN from 0.25 to 0.45, thickness of AlGaN cap layer, thickness of AlN channel layer, doping concentrations give rise to a significant change in the 2DEG transport and <i>C</i>~<i>V</i> characteristics of the device and its detail discussion are presented in this paper. The 2DEG density with the variation of Al_xGa_1−xN thickness and Al mole fraction (<i>x</i>) are in good agreement with the experimental results from the literature. <br/> <br/>Page(s): 416-422 Sun, 29 May 2011 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/11716 Title: Analysis of space charge field of sheet electron beam for compact high power and high frequency microwave devices <br/> <br/>Authors: Panda, Purna Chandra; Srivastava, Vishnu; Vohra, Anil <br/> <br/>Abstract: Importance of sheet beam technology and role of space charge field analysis for success of this technology have been studied. Space charge field of sheet electron beam has been investigated in three approaches. At first a simplified infinite width sheet and line model are given to investigate nature of variation of field, then analysis is done for finite width beam. Using a theoretical model in OPERA 3-D, simulation has been done to compare space charge field. Space charge field of sheet electron beam is compared with that for equivalent round beam. Interpretation is made about nature of space charge field and its impact to sheet beam transport. Importance of proper optimization of beam height has been emphasized. <br/> <br/>Page(s): 410-415 Sun, 29 May 2011 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/11715 Title: Space charge limited current in Schottky diode with single level traps <br/> <br/>Authors: Kumar, Pankaj; Jain, Anubha; Shukla, Manju; Chand, Suresh <br/> <br/>Abstract: The space charge limited current (SCLC) in a Schottky diode with a finite injection barrier at the injecting contact and single level traps in the energy space has been investigated by mathematical modelling. Solution of coupled Poisson’s and continuity equations with non-zero Schottky barrier (<img src='http://www.niscair.res.in/jinfo/phi.gif' border=0>) leaded us to calculate the electric field [<i>F</i>(<i>x</i>)] and the charge carrier <i style="">p</i>(<i style="">x</i>) distribution in the sample. Considering the boundary conditions, the current density-voltage (<i style="">J-V</i>) characteristics have been calculated numerically. It is reported here that when Schottky barrier is not zero, <i style="">J-V</i> characteristics become Ohmic at infinitely large voltages. The expression of trap filled limit voltage (<i style="">V_TFL</i>) has also been derived. The effect of Schottky barrier on the SCLC current in semiconducting devices has been studied in the present paper. <br/> <br/>Page(s): 406-409 Sun, 29 May 2011 22:58:59 GMT