Analog Electronic Circuits

Diode Basics and Equivalent Circuits

Question 1
Marks : +2 | -2
Pass Ratio : 43%
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?
0
5 mA
4.3 mA
Can’t be determined
Explanation:
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.
Question 2
Marks : +2 | -2
Pass Ratio : 14%
Which model of the diode equivalent circuit is represented by the given diagram?
Piecewise Linear Model
Ideal Diode Model
Simplified Model
Differential Model
Explanation:
This model involves a voltage drop and a resistance in series with an ideal diode and hence it represents the Piecewise Linear Model.
Question 3
Marks : +2 | -2
Pass Ratio : 29%
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?
4.3 mA
0
43 mA
5 mA
Explanation:
The diode in the circuit is reverse biased and hence the current is zero.
Question 4
Marks : +2 | -2
Pass Ratio : 14%
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?
True
False
Explanation:
During reverse bias operation of a diode, the width of the depletion region increases leading to extremely high values of resistance and hence negligible values of current.
Question 5
Marks : +2 | -2
Pass Ratio : 14%
What is the approximate value of voltage across the silicon diode for the diagram given?
+0.7 V
0 V
+10 V
-10 V
Explanation:
-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.
Question 6
Marks : +2 | -2
Pass Ratio : 14%
From the given I-V characteristics of a silicon diode, what is the approximate value of rav between marked points?
7 ohms
11.2 ohms
8 ohms
6 ohms
Explanation:
rav is the average AC resistance, found between two marked points in the I-V graph. Here rav=0.1/14mA=7Ω.
Question 7
Marks : +2 | -2
Pass Ratio : 29%
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, for the same diode voltage. Which of the following options hold true?
r1 = r2
r1 > r2
r1 < r2
Can’t be determined
Explanation:
r1 > r2 as AC resistance is inversely proportional to the diode current.
Question 8
Marks : +2 | -2
Pass Ratio : 14%
The reverse saturation current for a Germanium diode at a temperature of 293 K is found to be 2 μA. What is the reverse saturation current Is at a temperature of 313 K?
2 μA
8 μA
4 μA
Can’t be determined
Explanation:
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.
Question 9
Marks : +2 | -2
Pass Ratio : 43%
Which of the following models of diode equivalent circuit is represented by the given I-V characteristic curve?
Piecewise Linear Model
Ideal Diode Model
Simplified Model
Hybrid model
Explanation:
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.
Question 10
Marks : +2 | -2
Pass Ratio : 14%
Which of the following is not a valid form of a diode equivalent circuit?
Piecewise Linear Model
Ideal Diode Model
Simplified Model
Differential Model
Explanation:
Differential model doesn’t define any diode. It defines an Operational Amplifier.