### GATE Questions on "Zener Diode" (1987 to Till Date)

1988
1.       For a PN junction, match the type of breakdown with phenomenon
i.         Avalanche breakdown
ii.       Zener breakdown
iii.      Punch through

a.       Collision of carriers with crystal ions
b.      Early effect
c.       Rupture of covalent bond due to strong electric field

1989
1.       In a Zener diode,
a.       only P-region is heavily doped
b.      only N-region is heavily doped
c.       both P and N-regions are heavily doped
d.      both P and N-regions are lightly doped

1992
1.       The 6 volts Zener diode shown in figure has zero zener resistance and a knee current of 5 mA. The minimum value of R so that the voltage across it does not fall below 6 volts is ……

1993
1.       The wave shape of Vo in the figure will be

Solution :

1995

1.       A Zener diode works on the principle of
a.       Tunneling of charge carriers across the junction
b.      Thermionic emission
c.       Diffusion of charge carriers across the junction
d.      Hopping of charge carriers across the junction

1996

1.       A Zener diode in the circuit shown has a knee current of 5 mA, and a maximum allowed power dissipation of 300 mW. What are the minimum and maximum load currents that can be drawn safely from the circuit, keeping the output voltage Vo constant at 6 volts ?

a.       0 mA,  180 mA
b.      5 mA, 110 mA
c.       10 mA, 55 mA
d.      60 mA, 180 mA

1999

1.       A DC power supply has a no-load voltage of 30 volts, and a full load voltage of 25 volts at a full
load current of one amp. Its output resistance and load regulation, respectively are
a.       5 and 20 %
b.      25 and 20 %
c.       5 and 16.7 %
d.      25 and 16.7 %

2001

1.       The transistor shunt regulator shown in figure has a regulated output voltage of 10 volts, when input varies from 20 volts to 30 volts. The relevant parameters for the zener diode and the transistor are: VZ = 9.5 volts, VBE = 0.3 votls, β = 99. Neglect the current throught RB. Then the maximum power dissipated in the zener diode (PZ) and the transistor (PT) are

2002

1.       A zener diode regulator in figure, is to be designed to meet the specifications : IL = 10 mA, Vo = 10 volts and Vin varies from 30 to 50 volts. The zener diode has VZ = 10 volts and IZK (knee current) = 1 mA. For satisfactory operation

2004

1.   In the voltage regulator shown, the load current can vary from 100 mA to 500 mA. Assuming that the zener diode is ideal (i.e. the zener knee current is negligibly small and zener resistance is zero in the breakdown region), the value of R is

2005

1.       The zener diode in the regulator circuit shown has a zener voltage of 5.8 volts and a zener knee current of 0.5 mA. The maximum load current drawn from this circuit ensuring proper functioning over the input voltage range between 20 and 30 volts is

2006

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

2.   For the circuit shown below, assume the zener diode is ideal with a breakdown voltage of 6 volts. The waveform observed across R is

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.

2.   For the zener diode shown in the figure, the zener voltage at knee is 7 volts, the knee current is negligible and the zener dynamic resistance is 10 Ω. If the input voltage (Vi) range is 10 to 16 volts, the output voltage (Vo) ranges from

2008
1.       In the following limiter circuit, an input voltage Vi  = 10sin100πt applied. Assume that the diode drop is 0.7 volts when it is forward biased. The zener breakdown voltage is 6.8 volts.
The maximum and minimum values of the output voltage respectively are

a.       6.1 volts, -0.7 volts
b.      0.7 volts, -7.5 volts
c.       7.5 volts, -0.7 volts
d.      7.5 volts, -7.5 volts

2.   Consider the following assertions.
S1: For zener effect to occur, a very abrupt junction is required
S2: For quantum tunneling to occur, a very narrow energy barrier is required.
Which of the following is correct?
a.       Only S2 is true
b.      Both are true but S2 is not a reason for S1
c.       Both are true but S2 is a reason for S1
d.      Both are false

2011
1.       A Zener diode when used in voltage stabilization circuits, is biased in
a.       Reverse bias region below the breakdown voltage
b.      Reverse breakdown region
c.       Forward bias region
d.      Forward bias constant current mode

2013

1.       In the circuit shown below, the knee current of ideal zener diode is 10 mA. To maintain 5 volts across the load RL, the minimum value of RL in ’s and the minimum power rating of the zener diode in mW respectively are

a.       125 and 125
b.      125 and 250
c.       250 and 125
d.      250 and 250

2015

1.   In the circuit shown below, the Zener diode is ideal and the Zener voltage is 6 volts. The output voltage Vo (in volts) is _______________