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1. Which of the following is not a valid form of a diode equivalent circuit?
a) Piecewise Linear Model
b) Ideal Diode Model
c) Simplified Model
d) Differential Model

Answer: d [Reason:] Differential model doesn’t define any diode. It defines an Operational Amplifier.

2. Which model of the diode equivalent circuit is represented by the given diagram? a) Piecewise Linear Model
b) Ideal Diode Model
c) Simplified Model
d) None of the mentioned

Answer: a [Reason:] This model involves a voltage drop and a resistance in series with an ideal diode and hence it represents the Piecewise Linear Model.

3. From the given I-V characteristics of a silicon diode, what is the value of rav between marked points? a) 5 ohms
b) 11.2 ohms
c) 8 ohms
d) None of the mentioned

Answer: a [Reason:] rav. = change in diode voltage per change in diode current. Hence, rav = 0.075V/15mA = 5 ohms.

4. AC resistance of a diode was found to be r1 and r2, when measured with two different values of diode current i.e. 10 mA and 25 mA respectively. Which of the following options hold true?
a) r1 = r2
b) r1 > r2
c) r1 < r2
d) Can’t be determined.

Answer: b [Reason:] r1 > r2 as AC resistance is inversely proportional to the diode current.

5. Which of the following models of diode equivalent circuit is represented by the given I-V characteristic curve? a) Piecewise Linear Model
b) Ideal Diode Model
c) Simplified Model
d) None of the mentioned

Answer: c [Reason:] In simplified model, the value of rd is neglected and hence, we get a high value of current for voltage greater than or equal to VT.

6. What is the approximate value of voltage across the diode for the diagram given alongside? a) +0.7 V
b) -0.7 V
c) +10 V
d) -10 V

Answer: d [Reason:] -10 V. The operating characteristic of a diode operating in the reverse bias region suggests that beyond a certain threshold current, the voltage across the diode is nearly constant = reverse breakdown voltage.

7. Assuming the diode in the given circuit diagram to be a silicon p-n junction diode, what is the current for the given circuit diagram? a) 4.3 mA
b) 0
c) 43 mA
d) 5 mA

Answer: b [Reason:] The diode in the circuit is reverse biased and hence the current is zero.

8. Assuming the diode in the given circuit diagram to be a silicon p-n junction diode, what is the current for the given circuit diagram? a) 0
b) 5 mA
c) 4.3 mA
d) Can’t be determined

Answer: c [Reason:] 4.3 mA. The silicon diode in the circuit is forward biased. Considering a voltage drop of 0.7 V across the diode, the voltage drop across the resistor is (5-0.7) V = 4.3 V. Hence, Current in the circuit = Current through the resistor = (4.3/1000) A = 4.3 mA

9. The reverse saturation current for a Germanium diode at a temperature of 293 K is found to be 2 uA. What is the reverse saturation current Is at a temperature of 313 K?
a) 2 uA
b) 8 uA
c) 4 uA
d) Can’t be determined

Answer: b [Reason:] The reverse saturation current for a silicon diode doubles its value for every 10 K rise in temperature. Hence Is at 313 K=2 x 2 x 2 = 8 uA.

10. During the reverse bias operation of a p-n junction diode, the width of the depletion region increases. Is the given statement true or false?
a) True
b) False