GATE Questions on "Special Purpose Diodes (Tunnel diode, LED, PIN diode, Photo diode & LASER)" (1987 to Till Date)

1990

1. In a forward biased photo diode, with increase in incident light intensity, the diode current
       a.  increasees
       b.  remains constant
       c.  decreases
       d.  remains constant, but the voltage drop across the diode increases.
Answer:  A
Solution :  https://www.youtube.com/watch?v=dBkgMBzNyYA



2. SCR can be turned On by
       a. Applying anode voltage at sufficiently fast rate
       b. Applying sufficiently large anode voltage
       c. Increasing the temperature of SCR to a sufficiently large value
       d. Applying sufficiently large gate current

Answer:  All are correct, most accurate is D
 Solution :   https://www.youtube.com/watch?v=U0x31gFcggQ

1992

1.       An infrared LED is usually fabricated from

      a.       Ge

      b.      Si

      c.       GaAs

      d.      GaAsP

Answer:  C
                   Solution :  https://www.youtube.com/watch?v=fLphChzvpvo

2003

1.       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.

Answer: C

                Solutoin :  https://www.youtube.com/watch?v=GCy6rgwSBes

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

Answer: C

                Solutoin :  https://www.youtube.com/watch?v=O-KiCZLmIxo

3.   A particular green LED emits light of wavelength 5490 A^o. 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

Answer: A

                Solutoin :  https://www.youtube.com/watch?v=ece35Kq_7jI

2004

1.   The longest wavelength that can be absorbed by silicon, which has the band gap of 1.12 eV is 1.1 µm. If the longest wavelength that can be absorbed by another material is 0.87 µm, then the band gap of this material is

      a.       1.416 eV 

      b.      0.886 eV

      c.       0.854 eV

      d.      0.706 eV

Answer: A

                Solution : https://www.youtube.com/watch?v=wlIK6u3cSrE

2006

1.       The values of voltage across a tunnel diode (V_D) corresponding to peak and valley currents are V_P and V_V respectively. The range of tunnel diode voltage V_D for which the slope of its I-V characteristics is negative would be

Answer: C

               Solution : https://www.youtube.com/watch?v=k7NNJYXvEvk

2.       Find the correct match between Group 1 and Group 2 :

Answer: C

                Solution : https://www.youtube.com/watch?v=OkGp1dylZb4

2007

1.       Group I lists four types of PN junction diodes. Match each device in Group I with one of the option in Group II to indicate the bias condition of that device in its normal mode of operation.

Answer: B

               Solution :  https://www.youtube.com/watch?v=4KUze2mrsoo

2.       Group I lists four different semiconductor devices. Match each device in Group I with its characteristic property in Group II.

Answer:   C
  Solution :  https://www.youtube.com/watch?v=iwERJKn2hUU

2014

Set – 1 (15th February 2014 (Forenoon))

1.       When the optical power incident on a photo diode is 10 µW and the responsivity is 0.8 A/W, the photo current generated (in µA) is ____________.

Answer: 8

                  Solution :  https://www.youtube.com/watch?v=FdWts4kUgOI

2.       In the figure, assume that the forward voltage drops to the PN diode D₁ and Schottky diode D₂ are 0.7 volts and 0.3 volts respectively. If ON denotes conducting state of the diode and OFF denotes the non conducting state of the diode, then in the circuit,

      a.       Both are ON

      b.      D₁ is ON and D₂ is OFF

      c.       Both are OFF

      d.      D₁ is OFF and D₂ is ON

Answer: D

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

SET  - 4  (16th February 2014 (Afternoon))

1.       At T = 300^oK, the band gap and the intrinsic carrier concentration of GaAs are 1.42 eV and 10⁶ cm^-3 respectively. In order to generate electron hole pairs in GaAs, which one of the wavelength (λ_c) ranges of incident radiation, is most suitable? (Given that Plank’s constant = 6.62 x 10^-34 J-sec, velocity of light is 3 x 10¹⁰ cm/s and charge of electron is 1.6 x 10^-19C)

      a.       0.42 µm < λ_c < 0.87 µm

      b.      0.87 µm < λ_c < 1.42 µm

      c.       1.42 µm < λ_c < 1.62 µm

      d.      1.62 µm < λ_c < 6.62 µm

Answer: A

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

2.       The cutoff wavelength (in µm) of light that can be used for intrinsic excitation of a semiconductor material of band gap E_g = 1.1 eV is …………..

Answer: 1.12

                  Solution :  https://www.youtube.com/watch?v=bfF2NoqjjDU

2015