All Free Electrical Engineering MCQs with Answers

• A. Amplifier circuits
• B. Switching circuits
• C. Rectifier circuits
• D. None of the above

Explanation: The base-resistor method gives poor bias stability because collector current depends strongly on transistor beta, so it is mainly suitable…

• A. 25
• B. 50
• C. 100
• D. 200

Explanation: With fixed base bias, the collector current is approximately I_C = βI_B, so a change in beta produces a corresponding proportional change…

• A. Remains the same
• B. Decreases
• C. Increases
• D. None of the above

Explanation: For a common-emitter circuit, V_CE is approximately V_CC − I_C R_C. Therefore, with supply voltage and collector resistance fixed…

• A. Depends upon IC to moderate extent
• B. Is almost independent of IC
• C. Is strongly dependant on IC
• D. None of the above

Explanation: For a conducting transistor, V_BE changes only logarithmically with collector current, so over normal operating ranges it is treated as…

• A. 105 kO
• B. 530 kO
• C. 315 kO
• D. None of the above

Explanation: The base current is I_B = I_C/β = 1 mA/100 = 10 μA, and the base resistor is R_B = (V_CC − V_BE)/I_B = (6 − 0.7)/10 μA = 530 kΩ.

• A. Change in ICBO
• B. Change in VCC
• C. Change in the values of circuit resistance
• D. None of the above

Explanation: Temperature rise increases the reverse leakage current I_CBO, which increases collector current and shifts the transistor operating point.

• A. RE consideration
• B. RC consideration
• C. VCC consideration
• D. None of the above

Explanation: In the voltage-divider bias circuit, R_E provides negative feedback: increased collector or emitter current raises the emitter voltage and…

• A. VCE consideration
• B. VBE consideration
• C. IB consideration
• D. None of the above

Explanation: R_C is selected from the desired collector voltage and operating-point condition, using the voltage drop V_RC = I_C R_C and the required…

• A. VBE
• B. 2VBE
• C. 5 VBE
• D. None of the above

Explanation: Applying KVL across the collector-emitter path gives VCE = VCB + VBE. The collector-to-base and base-to-emitter voltages therefore add to…

• A. The same as
• B. More than
• C. Less than
• D. None of the above

Explanation: Collector-feedback bias provides negative feedback: an increase in collector current raises the feedback voltage and opposes the increase.

• A. Remains the same
• B. Is increased
• C. Is decreased
• D. None of the above

Explanation: As temperature rises, leakage current and collector current generally increase, causing a larger voltage drop across the collector…

• A. RB (ß+1)
• B. (ß+1)RC
• C. (ß+1)
• D. 1-ß

Explanation: For fixed base-resistor bias, the stability factor is S = 1 + β, commonly written as β + 1.

• A. 2000 O
• B. 1400 O
• C. 800 O
• D. 1600 O

Explanation: Using VCC = VRC + VCE + VE, the emitter voltage is 9 − (2 mA)(2.2 kΩ) − 3 = 1.6 V. Thus RE = VE/IE = 1.6 V/2 mA = 800 Ω.

• A. High stability factor
• B. Low base current
• C. Many resistors
• D. None of the above

Explanation: Voltage-divider bias is thermally stable, but it requires the divider, collector, and emitter resistors, making it more complex than…

• A. The end point
• B. Middle
• C. The maximum current point
• D. None of the above

Explanation: Placing the operating point near the midpoint of the DC load line allows nearly equal maximum swings toward cutoff and saturation.

• A. Cut off point
• B. Quiescent point
• C. Saturation point
• D. None of the above

Explanation: The operating point is the transistor's quiescent point, abbreviated Q-point, representing the zero-signal condition.

• A. 10 IB
• B. 3 IB
• C. 2 IB
• D. 4 IB

Explanation: For good voltage-divider bias stabilisation, the divider current I1 is commonly chosen as at least 10 times the base current IB.

• A. Is complicated
• B. Is sensitive to changes in ß
• C. Provides high stability
• D. None of the above

Explanation: In base-resistor bias, the collector current depends strongly on beta through IC approximately equal to beta times IB.

• A. One hundredth
• B. One tenth
• C. One thousandth
• D. One millionth

Explanation: Silicon has much lower minority-carrier leakage than germanium, commonly approximated as about one-thousandth under comparable conditions.

• A. 100 µA
• B. 25 µA
• C. 20 µA
• D. 50 µA

Explanation: The stability factor relates the collector-current change to the leakage-current change: S = ΔIC/ΔICBO. Therefore, ΔIC = 50 × 1 μA = 50 μA.