This set of Electronic Devices and Circuits Multiple Choice Questions & Answers (MCQs) focuses on “BJTs Current-Voltage Characteristics”.
1. The curve between the collector current versus the potential difference between the base and emitter is
a) A straight line inclined to the axes
b) A straight line parallel to the x-axis
c) An exponentially varying curve
d) A parabolic curve
View Answer
Explanation: The natural logarithm of the collector current depends directly on the the potential difference between the base and the emitter.
2. The curve between the collector current and the saturation is
a) A straight line inclined to the axes
b) A straight line parallel to the x-axis
c) A straight line parallel to the y-axis
d) An exponential curve
View Answer
Explanation: The collector current depends directly on the saturation current.
3. The magnitude of the thermal voltage is given by
a) k/Tq
b) kT/q
c) q/Kt
d) Tk/q
View Answer
Explanation: kT/q is the correct mathematical expression for the thermal voltage.
4. The correct relation between the transistor parameters α and ß are related by
a) ß = 1 – α/α
b) ß = 1 + α/α
c) α = ß + 1/ß
d) α = ß/ß + 1
View Answer
Explanation: Only expression α = ß/ß + 1 is the correct expression that relates α and ß.
5. The correct expression relating the emitter current Ie to the collector current Ic is
a) Ie = α Ic
b) Ic = α Ic
c) Ie = ß Ic
d) Ic = ß Ic
View Answer
Explanation: Ie = Ic/α or Ic = α Ie
6. The value of the thermal voltage at room temperature can be approximated as
a) 25 mV
b) 30 mV
c) 35 mV
d) 40 mV
View Answer
Explanation: Thermal voltage is given by kT/q which at T = 25 degrees Celsius is approximately 25 mV.
7. The correct relation between the emitter current Ie and the base current Ib is given by
a) Ib = (1 + α) Ie
b) Ib = (α – 1) Ie
c) Ie = (1 – ß) Ib
d) Ie = (1 + ß) Ib
View Answer
Explanation: The correct mathematical expression are Ie = (1 – ß) Ib and Ib = (1 – α) Ie respectively.
8. The Early Effect is also called as
a) Base-width modulation effect
b) Base-width amplification effect
c) Both of the mentioned
d) None of the mentioned
View Answer
Explanation: At a given value of vBE, increasing vCE increases the reverse-bias voltage on the collector–base junction, and thus increases the width of the depletion region of this junction. This in turn results in a decrease in the effective base width W. Also the saturation current is inversely proportional to the width, the saturation current will increase and also makes collector current increases proportionally. This is the Early Effect. For the reasons mentioned above, it is also known as the base-width modulation effect.
9. For the BJT to operate in active mode Collector-Base junction must be
a) Heavily doped
b) Must reversed bias
c) Must be forward bias
d) Lightly doped
View Answer
Explanation: The BJT operates in active mode when the collector-Base junction is reversed bias. Also doping cannot prevent saturation of the transistor.
10. Collector current (Ic) reaches zero when
a) Vce = Vt ln (Isc/I)
b) Vt = Vce ln (Isc/I)
c) Vce = Vt ln (I/Isc)
d) Vce = Vt ln (Isc + I/I)
View Answer
Explanation: Ic = Is exp (Vbe/Vt) – Isc exp(Vbc/Vt). In this expression put ic = 0 and simplify.
Sanfoundry Global Education & Learning Series – Electronic Devices and Circuits.
To practice all areas of Electronic Devices and Circuits, here is complete set of 1000+ Multiple Choice Questions and Answers.
