Free Electronics and Devices MCQs with Answers

• A. Only positive
• B. Only negative
• C. Both positive and negative
• D. None of the above

Explanation: The Wien network supplies frequency-selective positive feedback, while negative feedback controls the amplifier gain and stabilizes the…

• A. It has superior electrical properties
• B. It is easily available
• C. It is quite inexpensive
• D. None of the above

Explanation: Quartz has a high mechanical Q and excellent piezoelectric and frequency-stability properties, allowing highly stable oscillation.

• A. Wien-bridge
• B. Hartely
• C. Crystal
• D. Phase shift

Explanation: A Wien-bridge oscillator produces a low-distortion sinusoidal signal over an adjustable frequency range, making it suitable for…

• A. Increased 2 times
• B. Decreased 4 times
• C. Increased 4 times
• D. Decreased 2 times

Explanation: For an LC oscillator, f = 1/(2π√LC). Increasing L fourfold makes √L twice as large, so the oscillation frequency becomes half its original…

• A. A. By magnetic induction
• B. By a tickler coil
• C. From the centre of split capacitors
• D. None of the above

Explanation: A Colpitts oscillator uses two capacitors in series, and the junction of these split capacitors provides the feedback voltage.

• A. 1
• B. Greater than 1
• C. Less than 1
• D. Equal to attenuation of feedback circuit

Explanation: An oscillator must begin with a loop gain greater than unity so that the initially small signal grows.

• A. A phase shift around the feedback loop of 180o
• B. A gain around the feedback loop of one-third
• C. A phase shift around the feedback loop of 0o
• D. A gain around the feedback loop of less than 1

Explanation: The Barkhausen phase condition requires the net phase shift around the feedback loop to be 0° or an integral multiple of 360°.

• A. Rigidity
• B. Vibrations
• C. Low Q
• D. High Q

Explanation: A crystal has a very high Q factor, giving it sharp resonance and excellent frequency selectivity.

• A. L and C
• B. R, L and C
• C. R and C
• D. None of the above

Explanation: A phase-shift oscillator uses an RC network to provide the required frequency-dependent phase shift.

• A. Radio receivers
• B. Radio transmitters
• C. TV receivers
• D. None of the above

Explanation: The Hartley oscillator uses a tapped inductor and is widely used for generating radio-frequency signals, especially in radio receivers.

• A. Proportional to square of
• B. Directly proportional to
• C. Independent of the values of
• D. Inversely proportional to square root of

Explanation: An LC oscillator has f = 1/(2π√LC), so its frequency is inversely proportional to the square root of either inductance L or capacitance C.

• A. power into d.c. power
• B. power into a.c. power
• C. mechanical power into a.c. power
• D. none of the above

Explanation: An electronic oscillator uses a DC supply and feedback network to produce a periodic AC voltage or current.

• A. 50KHz
• B. 100KHz
• C. 1000/17KHz
• D. 1000/7.07KHz

Explanation: A 20 dB voltage gain corresponds to a linear gain of 10. The gain-bandwidth product is therefore divided by 10, giving a bandwidth of 1…

• A. 2
• B. 1
• C. 1/2
• D. 0

Explanation: CMRR = Ad/Ac, and 80 dB corresponds to a ratio of 10^(80/20) = 10,000. Thus Ac = 20,000/10,000 = 2.

• A. Non inverter
• B. Voltage follower
• C. Summer
• D. Difference amplifier

Explanation: A DAC combines weighted input currents or voltages, so it commonly uses an op-amp summing amplifier.

• A. A ramp
• B. A sinusoidal wave
• C. A rectangular wave
• D. A triangular wave with dc bias

Explanation: For an op-amp integrator, the output is proportional to the time integral of the input.

• A. Instrumentation amplifiers
• B. Voltage followers
• C. Voltage regulators
• D. Buffers

Explanation: An instrumentation amplifier is built from differential-amplifier stages so it can amplify the voltage difference between two inputs while…

• A. High and low
• B. Positive and negative
• C. Inverting and non inverting
• D. Differential ans non differential

Explanation: The two op-amp inputs are called the inverting and non-inverting terminals.

• A. Av + Ac
• B. Av / Ac
• C. 1 + Av / AC.
• D. Ac / Av

Explanation: CMRR compares differential gain with common-mode gain, so CMRR = Av/Ac, often expressed in decibels as 20 log10(Av/Ac).

• A. 4
• B. 3
• C. 2
• D. 1

Explanation: The equation Vo = V1 is implemented by a voltage follower, which connects the output directly to the inverting input and requires only one…