All Free Electrical Engineering MCQs with Answers
Every Electrical Engineering question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
3,143 questions · page 97 of 158
- A. the depletion-mode
- B. the enhancement-mode
- C. cut off
- D. saturation
Explanation: A positive VGS in an n-channel depletion MOSFET attracts additional electrons to the channel, enhancing its conductivity.
Correct answer: the enhancement-mode- A. cut off and saturation
- B. cut off and pinch-off
- C. and IDSS
- D. pinch-off and breakdown
Explanation: A JFET operates with nearly constant drain current after pinch-off and continues in this region until breakdown.
Correct answer: pinch-off and breakdown- A. is increased
- B. is decreased
- C. remains the same
- D. none of the above
Explanation: For the same applied drain voltage, a larger channel cross-sectional area provides a lower-resistance path, so more carriers flow and the…
Correct answer: is increased- A. 100 to 500 mA/V
- B. 500 to 1000 mA/V
- C. 0.5 to 30 mA/V
- D. above 1000 mA/V
Explanation: A typical JFET transconductance lies roughly between 0.5 and 30 mA/V, depending on the device and bias point.
Correct answer: 0.5 to 30 mA/V- A. O
- B. a few hundred O
- C. kO
- D. several MO
Explanation: The MOSFET gate is insulated by an oxide layer, so its dc gate current is nearly zero and its input impedance is extremely high, commonly…
Correct answer: several MO- A. many gate
- B. open gate
- C. insulated gate
- D. shorted gate
Explanation: A MOSFET has an insulated gate, unlike the reverse-biased semiconductor gate junction of a JFET.
Correct answer: insulated gate- A. capacitor
- B. battery
- C. generator
- D. none of the above
Explanation: The insulated gate and channel form a capacitor, and the capacitor's electric field changes the channel conductivity.
Correct answer: capacitor1928. If the gate of a JFET is made less negative, the width of the conducting channel__________________?
- A. remains the same
- B. is decreased
- C. is increased
- D. none of the above
Explanation: Making the n-channel JFET gate less negative reduces the reverse bias and narrows the depletion regions, leaving a wider conducting…
Correct answer: is increased- A. 5 V
- B. 0.6 V
- C. 15 V
- D. 25 V
Explanation: JFET pinch-off or cutoff voltage is device-dependent, but introductory texts commonly use about 5 V as a typical value.
Correct answer: 5 V- A. forward
- B. reverse
- C. not
- D. none of the above
Explanation: In class A operation, the JFET gate-channel junction is kept reverse biased so gate current remains almost zero while the device conducts…
Correct answer: reverse- A. anode
- B. cathode
- C. grid cut off
- D. none of the above
Explanation: The JFET gate voltage that cuts off channel current performs the same basic function as the grid-cutoff voltage in a vacuum tube.
Correct answer: grid cut off- A. triode
- B. ordinary trnsistor
- C. tetrode
- D. JFET
Explanation: A JFET has low noise because its gate junction is reverse biased and its operation involves majority carriers, producing less noise than a…
Correct answer: JFET- A. JFET
- B. MOSFET
- C. Crystal diode
- D. ordinary transistor
Explanation: A MOSFET has the highest input impedance because its insulated gate draws essentially no input current.
Correct answer: MOSFET- A. high input impedance and square-law property
- B. inexpensive and high output impedance
- C. low input impedance and high output impedance
- D. none of the above
Explanation: A JFET combines very high input impedance with a square-law drain-current characteristic in its active region.
Correct answer: high input impedance and square-law property1935. In a JFET, when drain voltage is equal to pinch-off voltage, the depletion layers ______________?
- A. almost touch each other
- B. have large gap
- C. have moderate gap
- D. none of the above
Explanation: At the pinch-off voltage, the depletion regions expand until they nearly meet at the drain end of the channel.
Correct answer: almost touch each other- A. it is made of semiconductor material
- B. input is reverse biased
- C. of impurity atoms
- D. none of the above
Explanation: The JFET gate-channel junction is reverse biased, so it permits only a very small leakage current and therefore presents high input…
Correct answer: input is reverse biased- A. small
- B. very high
- C. very small
- D. none of the above
Explanation: A JFET provides very high power gain because its high input impedance requires very little input power, while the drain circuit can…
Correct answer: very high- A. is decreased
- B. is increased
- C. remains the same
- D. none of the above
Explanation: Increasing the reverse gate bias widens the depletion regions around the channel.
Correct answer: is decreased- A. current
- B. voltage
- C. both current and voltage
- D. none of the above
Explanation: A JFET is voltage driven because the gate-to-source voltage controls channel width and hence drain current.
Correct answer: voltage- A. gate voltage
- B. source voltage
- C. drain voltage
- D. gate current
Explanation: The gate-to-source voltage is the input control parameter of a JFET because it controls the depletion-region width and therefore the…
Correct answer: gate voltage