GATE 1994 Electronic Devices (EDC) Video solutions

1.       A small concentration of minority carriers is injected into a homogeneous semiconductor crystal at one point. An electric field of 10 V/cm is applied across the crystal and this moves the minority carriers a distance of 1 cm in 20 µsec. The mobility in cm²/volt-sec will be

a.       1000

b.      2000

c.       5000

d.      50000

                Solution :  https://www.youtube.com/watch?v=Pe9nM75oo1U
 

2.       The threshold voltage of an n-channel MOSFET  can be increased by

a.       Increasing the channel dopant concentration

b.      Reducing the channel dopant concentration

c.       Reducing the gate oxide thickness

d.      Reducing the channel length

                 Solution :  https://www.youtube.com/watch?v=1C8CrsGguu0
 

3.       The forward dynamic resistance of a junction diode varies ……………… as the forward current.

                 Solution :  https://www.youtube.com/watch?v=HfjrpzG7j8s
 

4.       The transit time of the current carriers through the channel of an FET decides its ……………. characteristics.

                 Solution : https://www.youtube.com/watch?v=vQJjmHNsn3I

5.       A p-type silicon sample has a higher conductivity compared to an n-type sample having the same dopant concentration.  (TRUE / FALSE)

                Solution :  https://www.youtube.com/watch?v=WUKXrsePs-A
 

6.       Channel current is reduced on application of a more positive voltage to the gate of a depletion mode n-channel MOSFET.  (TRUE / FALSE)

                Solution :  https://www.youtube.com/watch?v=W34kWifl15o
 

7.       Match the following :

                 Solution : https://www.youtube.com/watch?v=GWjW0DVZkSI

8.       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/volt-sec, µ_p = 450 cm²/volt-sec, and the intrinsic carrier concentration, n_i = 1.5 X 10¹⁰ cm^-3.

     Solution :  https://www.youtube.com/watch?v=_O5iozGDyEM
 

9.  In the common emitter amplifier shown, the transistor has a forward current gain of 100, and a base to emitter voltage of 0.6 volts. Assume I_CO to be negligible. Choose value for R₁ and R₃ such that the transistor has a collector current of 1 mA and a collector to emitter voltage of 2.5 volts.

     Solution :    https://www.youtube.com/watch?v=SjV5f5WC8GU