### GATE 2003 ECE Video Solutions on EDC (Electronic Devices and Circuits)

1. N – Type silicon is obtained by doping silicon with
a. Germanium
b. Aluminum
c. Boron
d. Phosphorous

2. The band gap of silicon at 3000K is
a. 1.36 eV
b. 1.10 eV
c. 0.80 eV
d. 0.67 eV

3. The intrinsic carrier concentration of silicon sample at 300oK is 1.5 x 1016 m-3. If after doping, the number of majority carriers is 5 x 1020 m-3, the minority carrier density is
a. 4.5 x 1011 / m3
b. 3.3 x 104 / m3
c. 5 x 1020 / m3
d. 3 x 10-5 / m3

4. Choose proper substitutes for X and Y to make the following statement correct.
Tunnel diode and Avalanche photo diode are operated in X bias and Y bias respectively.
a. X: Revere , Y: Reverse
b. X: Revere, Y: Forward
c. X: Forward, Y: Reverse
d. X: Forward, Y: Forward

5. For an N channel type MOSFET, if the source is connected at a higher potential than that of the bulk (i.e. VSB > 0 volts), the threshold voltage VT of the MOSFET will
a. Remain unchanged
b. Decrease
c. Change polarity
d. Increase

6. An N type silicon bar 0.1 cm long and µm2 in cross sectional area has a majority carrier concentration of 5 x 1020 m-3 and the carrier mobility is 0.13 m2/V-sec at 300oK. If the charge of an electron is 1.6 x 10-19 coulomb, then the resistance of the bar is
a. 106
b. 104
c. 10-1
d. 10-4

7. The electron concentration in a sample of uniformly doped N type silicon at 300oK varies linearly from 1017 cm-3 at x = 0 µm to 6 x 1016 cm-3 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/sec, the current density in the silicon, if no electric field is present is
a. Zero
b. -112 A/cm2
c. +1120 A/cm2
d. -1120 A/cm2

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

9. 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 Ge to that of Si diode is
a. 1
b. 5
c. 4 x 103
d. 8 x 103

10. A particular green LED emits light of wavelength 5490 Ao. The energy band gap of the semiconductor material used there is (Plank’s constant = 6.626 x 1034 J-Sec)
a. 2.26 eV
b. 1.98 eV
c. 1.17 eV
d. 0.74 eV

11. When the gate to source voltage (VGS) of a MOSFET with threshold voltage of 400 mV. The drain current observed is 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

12. 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
a. P-Q-R-S
b. Q-S-R-P
c. R-P-S-Q
d. S-R-Q-P

13. 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 current source
d. Voltage controlled voltage source