This set of Power Electronics Multiple Choice Questions & Answers (MCQs) focuses on “Power Transistors – 1”
1. Which of the following devices does not belong to the transistor family?
a) IGBT
b) MOSFET
c) GTO
d) BJT
View Answer
Explanation: GTO is gate turn off transistor, it belongs to the Thyristor family. All the other devices belong to the transistor family.
2. A power transistor is a
a) three layer, three junction device
b) three layer, two junction device
c) two layer, one junction device
d) four layer, three junction device
View Answer
Explanation: It has three layers p-n-p or n-p-n forming two p-n junctions.
3. In a power transistor, ____ is the controlled parameter.
a) VBE
b) VCE
c) IB
d) IC
View Answer
Explanation: The collector current is the controlled parameter.
4. A power transistor is a _________ device.
a) two terminal, bipolar, voltage controlled
b) two terminal, unipolar, current controlled
c) three terminal, unipolar, voltage controlled
d) three terminal, bipolar, current controlled
View Answer
Explanation: Power transistor is simply many BJT’s connected in series parallel on a single silicon chip for power applications. It is a three terminal, bipolar, current controlled device.
5. In a power transistor, _________ is the controlling parameter.
a) VBE
b) VCE
c) IB
d) IC
View Answer
Explanation: The base current controls the collector current. Hence, the base current Ib is the controlling parameter.
6. In a power transistor, the IB vs VBE curve is
a) a parabolic curve
b) an exponentially decaying curve
c) resembling the diode curve
d) a straight line Y = IB
View Answer
Explanation: The B-E junction of a BJT resembles a p-n junction diode, hence the curve.
7. For a power transistor, if the base current IB is increased keeping VCE constant, then
a) IC increases
b) IC decreases
c) IC remains constant
d) none of the mentioned
View Answer
Explanation: Ic is directly proportional to Ic.
8. The forward current gain α is given by
a) IC/IB
b) IC/IE
c) IE/IC
d) IE/IB
View Answer
Explanation: Collector current by emitter current is the current gain, its value is close to one but never greater than.
9. The value of β is given by the expression
a) IC/IB
b) IC/IE
c) IE/IC
d) IE/IB
View Answer
Explanation: Collector current by the base current is beta, its value is in the range 50 to 300.
10. A power BJT is used as a power control switch by biasing it in the cut off region (off state) or in the saturation region (on state). In the on state
a) both the base-emitter & base-collector junctions are forward biased
b) the base-emitter junction is reverse biased, and the base collector junction is forward biased
c) the base-emitter junction is forward biased, and the base collector junction is reversed biased
d) both the base-collector & the base-emitter junctions are reversed biased
View Answer
Explanation: When base-emitter & base-collector junctions are forward biased only than both the p-n junctions are forward biased and the device is on.
Sanfoundry Global Education & Learning Series – Power Electronics.
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