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 µ_n = 1350 cm²/V-sec, µ_p = 450 cm²/V-sec, and the 

     intrinsic carrier concentration, n_i = 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 V_BE = 0.6 volts. Assume I_CO 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) 

    (V_O-V_in) as shown in the figure below. Evaluate the value of 

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

     at which V_O falls abruptly by ∆V_o = V_Tn + V_Tp.