Free Electronics and Devices MCQs with Answers

• A. Diode
• B. Transistor
• C. FET
• D. Capacitor

Explanation: Capacitors are most difficult to fabricate in an IC because useful capacitance requires relatively large chip area and carefully formed…

• A. common source configuration
• B. common drain configuration
• C. common gate configuration
• D. none of the above

Explanation: The common-base BJT and common-gate JFET both keep the input-output common terminal at AC ground.

• A. drain to source current
• B. drain to source current with gate shorted
• C. drain to source current with gate open
• D. none of the above

Explanation: IDSS is the drain-to-source current when the gate is shorted to the source, so VGS equals zero.

• A. 0 mA
• B. ID(on)
• C. maximum
• D. IDSS

Explanation: A p-channel enhancement MOSFET conducts only when VGS is sufficiently negative, below its negative threshold voltage.

• A. 20 mA
• B. 0 mA
• C. 40 mA
• D. 10 mA

Explanation: A depletion MOSFET conducts at VGS = 0 V because its channel exists without gate bias.

• A. at its widest point
• B. completely closed by the depletion region
• C. extremely narrow
• D. reverse baised

Explanation: At cutoff, the reverse-biased gate junction's depletion regions extend across the channel and stop majority-carrier flow.

• A. +4 V
• B. -4 V
• C. dependent on VGS
• D. data insufficient

Explanation: For the usual JFET convention, the pinch-off voltage Vp is the positive magnitude of the negative cutoff voltage: Vp = |VGS(off)| = 4 V.

• A. plate
• B. cathode
• C. grid
• D. none of the above

Explanation: The JFET source supplies or collects charge carriers, making it analogous to the cathode of a vacuum tube.

• A. gate and drain
• B. drain and source
• C. gate and source
• D. input and output

Explanation: The conducting JFET channel provides the path through which drain current flows, so it lies between the drain and source terminals.

• A. pentode
• B. tetrode
• C. triode
• D. diode

Explanation: A JFET has a nearly constant-current region after pinch-off, where increasing drain voltage produces little additional current.

• A. three
• B. four
• C. five
• D. two

Explanation: A JFET has a channel bordered by the gate on two sides, forming two gate-channel pn junctions.

• A. cut off
• B. VDD
• C. VP
• D. V

Explanation: With VGS = 0, the JFET reaches pinch-off when VDS exceeds the pinch-off voltage VP, after which the drain current is approximately…

• A. of power rating
• B. the MOSFET has two gates
• C. the JFET has a pn junction
• D. none of the above

Explanation: A JFET controls its channel through a reverse-biased pn junction, whereas a MOSFET uses an insulated metal-oxide gate.

• A. 180o out of phase with the input
• B. in phase with the input
• C. 90o out of phase with the input
• D. taken at the source

Explanation: In a common-source amplifier, an increase in drain current produces a larger voltage drop across the drain resistor, making the drain…

• A. 2.05 V
• B. 25 V
• C. 0.5 V
• D. 1.89 V

Explanation: The effective drain load is 820 Ω || 10 kΩ ≈ 758 Ω, so Av ≈ gm(RD || RL) = 0.005 × 758 ≈ 3.79.

• A. 1
• B. 11.4
• C. 8.75
• D. 3.2

Explanation: Voltage gain is the ratio of output rms voltage to input rms voltage: Av = 3.2/0.280 ≈ 11.4. Therefore option b matches the calculated gain.

• A. the voltage gain will increase
• B. the transconductance will increase
• C. the voltage gain will decrease
• D. the Q-point will shift

Explanation: Removing the source bypass capacitor introduces source degeneration through the source resistor, reducing the AC voltage gain.

• A. increase
• B. decrease
• C. stay the same
• D. be zero

Explanation: Removing the load makes the effective drain resistance larger because the external load is no longer in parallel with the drain resistor.

• 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.

• 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.