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# Previous Year GATE Questions on Diode Applications

Last Updated - March 31, 2017

IIT Roorkee is the organizing authority for GATE 2017 exam. GATE 2017 is scheduled from February 4 – 12, 2017. The exam is held for 23 papers. A total of 65 questions carrying 100 marks are asked in GATE. There are 2 types of questions- Objective Type and Numerical Aptitude Type (NAT). In NAT questions, answers should be entered with the help of virtual keyboard.

Candidates should follow a proper study schedule to enhance their preparation. Practicing previous years’ questions gives the idea of level of questions and it increases the chance of scoring high marks in exam. Always try to solve the questions which are less time consuming. GATE is more about speed and accuracy. So, it is important to practice previous years’ questions.

Diodes and its applications cover a vast syllabus in Electrical and Tele Communication Engineering, Electrical Engineering and Instrumentation Engineering. Over the years, it has been observed that around 1-2 questions every year were asked from Diode and its applications.

The simplest semiconductor component, the diode, has an astounding number of applications that are enabled by a number of practical and unique types of diodes that are vital in modern electronics.

Previous years’ GATE questions on Diode Applications along with their solutions are provided below.

#### 1990

Q 1. For the same a.c. voltage and load impedance, which of the following statements about rectifier are correct?

1. The average load current in a full wave rectifier is twice than in a half wave rectifier
2. The average load current in a full wave rectifier is n times that in a half wave rectifier
3. Half wave rectifier will have a bigger sized transformer compared to full wave rectifier
4. Half wave rectifier will have a small sized transformer compared to full wave rectifier

For Solution Check the – Video

#### 1994

Q 1. A Ramp voltage v(t) = 100t volts is applied to a RC differentiating circuit with R = 5 kΩ and C = 4 µF. The maximum output voltage is ______

1. 0.2 volts
2. 2.0 volts
3. 10.0 volts
4. 50.0 volts

For Solution Check the – Video

Q 2. A pulse having a rise time of 40 nsec is displayed on a CRO of 12 MHz bandwidth. The rise time of the pulse as observed on the CRO would be approximately equal to ____________

For Solution Check the – Video

#### 1996

Q 1. In the circuit of the given figure, assume that the diodes are ideal and the meter is an average indicating ammeter. The ammeter will read ________

For Solution Check the – Video

#### 1997

Q 1. A half wave rectifier uses a diode with a forward resistance Rf. The voltage is Vmsinωt and the load resistance is RL. The DC current is given by

For Solution Check the – Video

#### 1998

Q 1. For full wave rectification, a four diode bridge rectifier is claimed to have the following advantages over a two diode circuit:

1. Less expensive transformer
2. Smaller size transformer, and
3. Suitability for higher voltage application.

Of these,

1. Only 1 and 2 are true
2. Only 1 and 3 are true
3. Only 2 and 3 true
4. 1, 2 as well as 3 are true

For Solution Check the – Video

Q 2. For small signal ac operation, a practical forward biased diode can be modeled as

1. Resistance and capacitance in series
2. Ideal diode and resistance in parallel
3. Resistance and ideal diode in series
4. Resistance

For Solution Check the – Video

Q 3. For the circuit shown,

1. Draw the transfer characteristics if both diodes D1 and D2 are ideal.
2. How would the characteristics change, if D2 is ideal but D1 is non-ideal? Assume D1 has forward resistance of 10 Ω and a reverse resistance of infinity.

For Solution Check the – Video

#### 2000

Q 1. a. For the circuit shown, plot Vo under steady state conditions, with and without capacitor C. Assume that the diode is ideal.

Answer: With Capacitor, circuit acts as Envelope Detector and Without capacitor, circuit acts as clipper which clips negative half cycle.

For Solution Check the – Video
b. Design a circuit using two ideal diodes, one resistor and two voltage sources that would convert the input voltage to the output voltage as shown in figure. The resistor value need not be specified.

For Solution Check the – Video

#### 2002

Q 1. A triangular voltage waveform Vi(t) is applied at the input to the circuit shown. Assume the diodes to be ideal.

1. Determine the output Vo(t)
2. Neatly sketch the output waveform superimposed on the input Vi(t) and label the key points.

For Solution Check the – Video

#### 2003

Q 1. The circuit shown in the figure is best described as a

1. Bridge rectifier
2. Ring modulator
3. Frequency discriminator
4. Voltage doubler

For Solution Check the – Video

#### 2004

Q 1. In the full wave rectifier using two ideal diodes, Vdc and Vm are the dc and peak values of the voltage respectively across a resistive load. If PIV is the peak inverse voltage of the diode, then the appropriate relationships for this rectifier are

For Solution Check the – Video

#### 2005

Q 1. A square pulse of 3 volts amplitude is applied to RC circuit shown in figure. The capacitor is initially uncharged. The output voltage Vo at time t = 2 sec is

1. 3 volts
2. –3 volts
3. 4 volts
4. –4 volts

#### 2011

In the circuit shown below, assume that the voltage drop across a forward biased diode is 0.7 votls. The thermal voltage VT = KT/q = 25 mV. The small signal input vi = 100 cos(ωt) mV.

Q1. The bias current IDC through the diodes is

1. 1 mA
2. 1.28 mA
3. 1.5 mA
4. 2 mA

Q 2. The ac output voltage VAC is

1. 0.25 cos(ωt) mV
2. 1 cos(ωt) mV
3. 2 cos(ωt) mV
4. 22 cos(ωt) mV

For Solution Check the – Video

#### 2013

Q 1. A voltage 1000sinωt volts is applied across YZ. Assuming ideal diodes, the voltage measured across WX in volts is

1. Sinωt
2. (Sinωt + |Sinωt|) / 2
3. (Sinωt - |Sinωt|) / 2
4. 0 for all t

For Solution Check the – Video

Q 2. 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 Ω’s and the minimum power rating of the Zener diode in mW respectively are

1. 125 and 125
2. 125 and 250
3. 250 and 125
4. 250 and 250

For Solution Check the – Video

#### 2014

Q 1. 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,

1. Both are ON
2. D1 is ON and D2 is OFF
3. Both are OFF
4. D1 is OFF and D2 is ON

For Solution Check the – Video

Q 2. The diode in the circuit shown, if Von = 0.7 volts but is ideal otherwise. If Vi= 5 sin(ωt) volts, the minimum and maximum values of Vo (in volts) are, respectively,

1. -5 and 2.7
2. 2.7 and 5
3. -5 and 3.85
4. 1.3 and 5

For Solution Check the – Video

Q 3. The figure shows a half wave rectifier. The diode D is ideal. The average steady state current (in Amperes) through the diode is approximately…………

For Solution Check the – Video

Q 4. Two silicon diodes, with a forward voltage drop of 0.7 volts, are used in the circuit shown in the figure. The range of input voltage Vi for which the output voltage Vo = Vi, is

1. -0.3 volts < Vi  < 1.3 volts
2. -0.3 volts < Vi  < 2 volts
3. -1.0 volts < Vi  < 2.0 volts
4. -1.7 volts < Vi  < 2.7 volts

For Solution Check the – Video

#### 2015

Q 1. If the circuit shown has to function as a clamping circuit, then which one of the following conditions should be satisfied for the sinusoidal signal of period T?

For Solution Check the – Video

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