Thursday, 6 June 2013

Video Solutions for GATE 2003 ECE : Two Mark Questions (Electron Devices)

1. An n-type silicon bar 0.1 cm long and µm2 in cross sectional 

    area  has a majority carrier concentration of 5 x 1020 /m3 and the

    carrier mobility is 0.13 m2/V-s at 3000K. if the charge of an 

    electron is 1.6x10-19 coulomb, then the resistance of the bar is

2. The electron concentration in a sample of uniformly doped 

    n-type silicon at 300oK varies linearly from 1017 /cm3 

    at x = 0 µm to 6 x 1016 /cm3 at x = 2 µm. Assume a situation 

    that electrons are supplied to keep this concentration gradient 

    constant with time. If electronic charge is 1.6 x 10-19 coulomb 

    and the diffusion constant Dn = 35 cm2/s, the current density in 

    the silicon, if no electric field is present, is 


3. Match items in Group 1 with items in Group 2, most suitably.


4. At 300oK, for a diode current of 1 mA, a certain germanium 

    diode requires a forward bias of 0.1435 volts, where as a certain

    silicon diode requires a forward bias of 0.718 volts. Under the 

    conditions stated above, the closest approximation of the ratio of 

    reverse saturation current in germanium diode to that of silicon 

    diode is 

   (A)  1            (B)  5                (C)   4 x103               (D)  8 x103


 5. A particular green LED emits light of wavelength 5490oA. 

     The energy band gap of the semiconductor material used there 

     is (Planck’s constant = 6.626x10-34 J-s) 

             (A)   2.26 eV                              (B)      1.98 eV   
             (C)     1.17 eV                            (D)     0.74 eV

6. When the gate to source voltage (VGS) of a MOSFET with 

     threshold voltage of 400 mV, working in saturation is 900 mV,

     the drain current in observed to be 1 mA. Neglecting the 

     channel length modulation effect, and assuming that the 

     MOSFET is operating at saturation, the drain current for
     an applied VGS of 1400 mV is 

             (A)     0.5 mA                 (B)       2.0 mA     

             (C)     3.5 mA                 (D)      4.0 mA

7. If P is Passivation, Q is n-well implant, R is metallization and 

    S is source/drain diffusion, then the order in which they are 

    carried out in a standard n-well CMOS fabrication process, is

8. The action of a JFET in its equivalent circuit can best be 

     represented as a 

                       (A)   Current controlled current source

                (B)   Current controlled voltage source

                (C)   Voltage controlled voltage source

                (D)   Voltage controlled voltage source




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