Junction Field Effect Transistor MCQ

Get all the Junction Field Effect Transistor MCQ which have already been asked in previous Engineering service Examinations (ESE) papers or this may come in upcoming exams also. So we have arranged almost all previous papers’ MCQs with answers and explanations given here.

Junction Field Effect Transistor MCQ

Que.1 The transconductance ‘g_m‘ of a JFET is equal to

(a) $-\frac{2I_{DSS}}{V_P}$
(b) $\frac{2}{|V_P|}\sqrt{I_{DSS}I_{DS}}$
(c) $-\frac{2I_{DS}}{V_P}$
(d) $\frac{I_{DSS}}{V_P} \left( 1-\frac{V_{GS}}{V_P} \right )$

Answer: (b) $\frac{2}{|V_P|}\sqrt{I_{DSS}I_{DS}}$

2. In a biased JFET, the shape of the channel is as shown in the given figure because

(a) It is the property of the material used
(b) the drain end is more reverse biased than the source end
(c) the drain end is more forward biased than the source end
(d) the impurity profile varies with the distance from the source

Answer: (b) the drain end is more reverse biased than the source end

3. The output current versus input voltage transfer characteristics of an n-channel JFET is such that there is

(a) zero current flow at zero input voltage bias
(b) current flow only when a positive input threshold voltage is crossed
(c)current flow only when a negative input cutoff voltage bias crossed
(d) no cutoff input voltage

Answer: (c)current flow only when a negative input cutoff voltage bias crossed

4. Which one of the following statements is correct, for a MOS capacitor fabricated on a p-type semiconductor, a strong inversion occurs when the surface potential is

(a) equal to Fermi potential
(b) zero
(c) negative and equal to Fermi potential in magnitude
(d) positive and equal to Fermi potential in magnitude

Answer: (d) positive and equal to fermi potential in magnitude

5. How is an N-channel junction field effect transistor operated as an amplifier?

(a) with a forward bias gate-source junction
(b) with a reverse bias gate-source junction
(c) with an open-source junction
(d) with a shorted gate-source junction

Answer: (b) with a reverse bias gate-source junction

6. In amOSFET, the transfer characteristics can be used to determine which of the following device parameters:

(a) Thereshold voltage and output
(b) transconductance and output resistance
(c) Thereshold voltage and transconductance
(d) transconductance and channel length modulation parameter

Answer: (c) Threshold voltage and transconductance

7. In n-channel enhancement MOSFET at a fixed drain voltage

(a) the drain current is maximum at zero gate voltage and it decreases with applied negative gate voltage
(b) the drain current has a finite value at zero gate voltage and it increases or decreases with the applied voltage of a proper polarity
(c) the drain current is zero at zero gate voltage and it increases with the positive applied gate voltage
(d) the drain current is zero for negative bias voltage to the gate and it increases as the negative gate bias is decreased in magnitude

Answer: (c) the drain current is zero at zero gate voltage and it increases with the positive applied gate voltage

8. A junction FET can be used as a voltage variable resistor

(a) at pinch-off condition
(b) beyond pinch-off voltage
(c) well below pinch-off condition
(d) for any value of V_DS

Answer: (c) well below pinch-off condition

9. Which one of the following statements is correct for MOSFETs?

(a) p-channel MOS is easier to produce than n-channel MOS
(b) n-channel MOS must have twice the area of p-channel MOS for the same ON resistance
(c) p-channel MOS has faster switching action than n-channel MOS
(d) p-channel MOS has a higher packing density than n-channel MOS

Answer: (a) p-channel MOS is easier to produce than n-channel MOS

10. which of the following devices is used in the microprocessor?

(a) JFET
(b) BJT
(c) MOSFET
(d) CMOS

Answer: (d) CMOS

11. Body effect is MOSFET results in

(a) increase in the value of transconductance
(b) change in the value of the threshold
(c) decrease in the value of transconductance
(d) increase in the value of output resistance

Answer: (b) change in the value of the threshold

12. In a JFET, operating above pinch-off voltage, the

(a) drain current increases steeply
(b) drain current remains practically constant
(c) drain current starts decreasing
(d) depletion region reduces

Answer: (b) drain current remains practically constant

13. What are the advantages of MOS transistor structure in integrated circuits?

(a) Faster switching
(b) Less capacitance
(c) Higher component density and lower cost
(d) Lower resistance

Answer: (c) Higher component density and lower cost

14. In JFET, when operated above the pinch-off voltage, the

(a) Depletion region becomes smaller
(b) Drain current starts decreasing
(c) Drain current remains practically constant
(d) Drain current increases steeply

Answer: (c) Drain current remains practically constant

15. In a MOS capacitance fabricated on a p-type semiconductor, strong inversion occurs, when potential is

(a) Equal to Fermi level
(b) Zero
(c) Negative and equal to Fermi potential in magnitude
(d) Positive and equal to Fermi potential in magnitude

Answer: (d) Positive and equal to Fermi potential in magnitude

16. For JFET, the drain current I_D is

(a) $I_{DSS} \left( 1 - \frac{V_{GS}}{V_p} \right )^{1/2}$
(b) $I_{DSS} \left( 1 - \frac{V_{GS}}{V_p} \right )$
(c) $I_{DSS} \left( 1 - \frac{V_{GS}}{V_p} \right )^{3/2}$
(d) $I_{DSS} \left( 1 - \frac{V_{GS}}{V_p} \right )^{2}$

Answer: (d) $I_{DSS} \left( 1 - \frac{V_{GS}}{V_p} \right )^{2}$

17. For n-channel depletion MOSFET, the highest transconductance gain for small signal is at

(a) V_GS = 0 V
(b) V_GS = V_p
(c) V_GS = |V_p|
(d) V_GS = – V_p

Answer: (a) V_GS = 0 V

Also Read:

Junction Field Effect Transistor MCQ

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