Tuesday, 11 June 2013

Video Solutions for GATE 1994 ECE : Five Mark Questions ( Electron Devices )




1. Show that the minimum conductivity of an extrinsic silicon 
    sample occurs when it is slightly p-type. Calculate the electron 
    and hole concentrations when the conductivity is minimum.


    Given that µn = 1350 cm2/V-sec, µp = 450 cm2/V-sec, and the 
     intrinsic carrier concentration, ni = 1.5x1010 cm-3.
Ans : hole concentration = 2.59 x 1010 cm-3.
        electron concentration = 0.866 x 1010 cm-3.








2. In the common emitter amplifier shown in the figure below, the

    transistor has a forward current gain of 100, and a base-emitter 

    voltage of VBE = 0.6 volts. Assume ICO to be negligible. 

    Choose value of R1 and R3 such that the transistor has a   

    collector  of  1 mA and a collector to emitter voltage of 2.5 volts.

Ans :  R1 = 41 K  and  R3 = 2.2 K

 
  


3. A typical CMOS interval has the transfer characteristics (VTC) 

    (VO-Vin) as shown in the figure below. Evaluate the value of 

     the inverter threshold VINV, which is the value of the input

     at which VO falls abruptly by ∆Vo = VTn + VTp.










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