Thursday, 6 June 2013

video Solutions for GATE 2008 ECE : Two Mark Questions ( Electron Devices )

1.  For the circuit shown in the following figure, transistors M1 and
     M2 are identical nMOS transistors. Assume that M2  is in 
    saturation and the output is unloaded . The current Ix is related   
    to I bias as 

2.  The measured transconductance  gm of an NMOS transistor 
     operating in the linear region is plotted against the gate voltage 
     VG at constant drain voltage VD. Which of the following figures 
      represents the expected dependence  of gm on VG ?

3.  Two identical NMOS transistors M1 and M2 are connected as 

      shown below. Vbias is chosen so that both transistors are in 

      saturation. The equivalent gm of the pair is defined to be 

     (dIout / dVi ) at constant Vout. The equivalent gm of the pair is

4.  Silicon is doped with boron to a concentration of 4 x 1017 

     atoms /cm3. Assuming the intrinsic carrier concentration of  

     silicon to be 1.5 x 1010 / cm3 and the value of KT/q to be 25mV 

     at 300oK. compared to undoped silicon, the Fermi level of  

     doped  silicon

5. The cross section of a JFET is shown in the following figure. 

    Let VG be -2 volts and let Vp be the initial pinch off voltage.

    If the width W is doubled  (with other geometric parameters 

    and doping levels remaining the same), then the ratio between 

    the mutual transconductance of the initial and the modified  

    JFET  is

6.  Consider the following assertions.

                S1 : For Zener effect to occur, a very abrupt junction is  

                S2 : For quantum tunneling to occur, a very narrow 
                       energy barrier is required .

    Which of the following is correct ?

(A)   Only S2 is true

(B)   S1 and S2 are both true but S2 is not a reason for S1 

(C)   S1 and S2 are both true but S2 is  a reason for S1

(D)   Both S1 and S2 are false

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