Analog Electronic Circuits

Types of Diode and their Testing

Question 1
Marks : +2 | -2
Pass Ratio : 100%
A diode on being checked by a DDM with diode checking function results in an open loop indication in both directions. Which of the following is the correct inference drawn from the given situation?
Power failure to the DDM
Diode is faulty
Diode is proper
Device isn’t connected properly
Explanation:
A diode allows electrical conduction in just one direction. Hence, if an instrument shows an open loop indication in both the directions, then the diode is faulty.
Question 2
Marks : +2 | -2
Pass Ratio : 100%
How can the location of the Zener region be controlled in the diode characteristic curve?
By changing the value of Iz
By changing the doping concentration of the diode
By changing the operating temperature
By increasing the size of diode
Explanation:
An increase in doping will lead to an increase in the concentration of impurities, which would further lead to a change in VZ and hence change in the Zener region.
Question 3
Marks : +2 | -2
Pass Ratio : 100%
Which of the following equipment can’t be used to check the condition of a diode?
Digital Display Meter
Ohmmeter
Curve Tracer
CRO
Explanation:
All the methods may be used to test a diode for its proper functioning except CRO.
Question 4
Marks : +2 | -2
Pass Ratio : 100%
What is the expected reading obtained on a Digital Display Meter with diode-checking function when a proper functioning silicon semiconductor diode is connected across its leads in the forward bias configuration?
0.67 V
0.3 V
Open Loop Indication
Varies with the diode
Explanation:
The diode checking function on the meter when used causes a current of 2 mA to flow through the diode and hence under forward bias, the voltage is determined to be 0.67 V. Germanium diodes show a drop around 0.3V.
Question 5
Marks : +2 | -2
Pass Ratio : 100%
A silicon semiconductor diode when subjected to ohmmeter testing gives low resistance in both directions. Which of the following is the correct inference to be drawn?
Diode is faulty
Power failure to the Ohmmeter
Diode is short-circuited
Diode is open circuited
Explanation:
A proper diode gives a low resistance reading along one direction and high resistance reading along the other. Hence, if diode gives low resistance readings in both directions, then the diode must be short-circuited. It’s noteworthy that a faulty diode gives a high resistance reading along both paths.
Question 6
Marks : +2 | -2
Pass Ratio : 100%
A silicon semiconductor diode when subjected to ohmmeter testing gives high resistance in both directions. Which of the following is the correct inference to be drawn?
Diode is faulty
Power failure to the Ohmmeter
Diode is short-circuited
Diode is open circuited
Explanation:
A proper diode gives a low resistance reading along one direction and high resistance reading along the other. Hence, if diode gives high resistance readings in both directions, then the diode must be faulty.
Question 7
Marks : +2 | -2
Pass Ratio : 100%
What is the expected reading obtained on a Digital Display Meter with diode-checking function when a proper functioning silicon semiconductor diode is connected across its leads in the reverse bias configuration?
0.67 V
0.3 V
Open Loop Indication
Varies with the diode
Explanation:
The diode checking function on the meter when used causes a current of 2 mA to flow through the diode and hence under reverse bias, the result obtained is the open loop indication.
Question 8
Marks : +2 | -2
Pass Ratio : 100%
Which material is generally used for the manufacture of Zener diode?
Silicon
Germanium
Mercury
Arsenic
Explanation:
Because of its high heat and current handling capacity, Silicon is generally used for the manufacture of Zener diodes.
Question 9
Marks : +2 | -2
Pass Ratio : 100%
Which of the following is not a part of the equivalent circuit of a Zener diode?
Dynamic Resistance
DC Battery
Ideal diode
Piecewise linear model of diode
Explanation:
The equivalent circuit diagram of a Zener diode doesn’t involve an ideal diode as it is used under reverse bias and an ideal diode doesn’t conduct under reverse bias.
Question 10
Marks : +2 | -2
Pass Ratio : 100%
At 298 K, the nominal Zener voltage is found to be equal to 10 V. Given that the value of the temperature coefficient is 0.072 (%/K), what is the nominal Zener Voltage at 398 K?
9.46 V
9.54 V
0.54 V
10.54 V
Explanation:
The change in VZ with temperature is calculated from the following equation: