# Multiple Choice Questions and Answers on Analog Electronics

**Q1. Which of the following oscillators is suitable for frequencies in the range of** **mega hertz?**

- RC phase shift
- Wien bridge
- Hartley
- Both (1) and (3)

**Answer. 3**

**Explanation: Only LC oscillators are suitable for MHz range**

**Q2. For a base current of 10 μA, what is the value of collector current in common emitter if β _{dc} = 100**

- 10 μA
- 100 μA
- 10 mA
- 1 mA

**Answer. 4**

**Explanation: I _{C} = 10 x 100 μA = 1 mA**

**Q3. To prevent a DC return between source and load, it is necessary to use ………………**

- resistor between source and load
- inductor between source and load
- capacitor between source and load
- either (1) or (2)

**Answer. 3**

**Explanation: Capacitor offers infinite impedance to DC**

**Q4. A half wave diode circuit using an ideal diode has an input voltage 20 sin ω t volts. Then average and rms values of output voltage are ………… and ……………**

**Answer. 2**

**Explanation: **

**Q5. If the input to the ideal comparator shown in the figure is a sinusoidal signal of 8 V (peak to peak) without any DC component, then the output of the comparator has a duty cycle of …………**

- 1/2
- 1/3
- 1/6
- 1/12

**Answer. 2**

**Explanation: **

**Q6. If an amplifier with a gain of – 1000 and feedback factor β = – 0.1 had a gain change of 20% due to temperature, the change in the gain of the feedback amplifier would be …………….**

- 10%
- 5%
- 0.2%
- 0.01%

**Answer. 3**

**Explanation:**

**Q7. The load impedance Z _{L} of a CE amplifier has R and L in series. The phase difference between output and input will be ………….**

- 180°
- 0
- more than 90° but less than 180°
- more than 180° but less than 270°

**Answer. 4**

**Explanation: It is 180° for purely resistive load and between 180° and 270° for R-L load**

**Q8. An RC coupled amplifier has an open loop gain of 200 and a lower cutoff frequency of 50 Hz. If negative feedback with β = 0.1 is used, the lower cut off frequency will be ……………**

- about 50 Hz
- about 5 Hz
- about 2.38 Hz
- about 70.5 Hz

**Answer. 3**

**Explanation:**

**Q9. Gain of the amplifier is ‘A’. Then the I/P impedance and O/P impedance of the closed loop amplifier shown below would be …………**

**Answer. 2**

**Explanation:**

**Q10. In the figure below v_{1} = 8 V and v_{2} = 4 V. Which diode will conduct?**

- D
_{2}only - D
_{1}only - Both D
_{1}and D_{2} - Neither D
_{1}nor D_{2}

**Answer. 2**

**Explanation:**

D_{1} will conduct and the output voltage will be about 7 V. Therefore D_{2} will be reverse biased and will not conduct.

**Q11. The action of JFET in its equivalent circuit can best be represented as a**

- current controlled current source
- current controlled voltage source
- voltage controlled voltage source
- voltage controlled current source

**Answer. 4**

**Q12. In a CB amplifier the maximum efficiency could be**

- 99%
- 85%
- 50%
- 25%

**Answer. 4**

**Q13. In a pn junction diode under reverse bias, the magnitude of electric field is maximum at **

- the edge of the depletion region on the p side
- the edge of the depletion region on the n side
- the pn junction
- the center of the depletion region on the n side

**Answer.** **3**

**Q14. To prevent a DC return between source and load , it is necessary to use ………….**

- resistor between source and load
- inductor between source and load
- capacitor between source and load
- both 1 and 2

**Answer.** **3**

**Q15. The cascade amplifier is a multistage configuration of ………….**

- CC-CB
- CE-CB
- CB-CC
- CE-CC

**Answer.** **2**

**Q16. which of the following statement is true ?**

**Negative feedback in an amplifier **

- reduces gain
- increase frequency and phase distortion
- reduces bandwidth
- increases noise

**Answer.** **1**

**Q17. The most commonly used amplifier in sample and hold circuit is ……………**

- a unity gain non-inverting amplifier
- a unity gain inverting amplifier
- an inverting amplifier with a gain of 10
- an inverting amplifier with a gain of 100

**Answer.** **2**

**Q18. In a common-emitter, unbypassed resistor provides ………….**

- voltage shunt feedback
- current series feedback
- negative voltage feedback
- positive current feedback

**Answer. 3**

**Q19. The current gain of a bipolar transistor drops at high frequencies because of …………..**

- Transistor capacitances
- High current effects in the base
- Parasitic inductive elements
- the early effect

**Answer. 1**

**Q20. Generally, the gain of a transistor amplifier falls at high frequencies due to …………….**

- Internal capacitance of the device
- Coupling capacitor at the input
- Skin effect
- Coupling capacitor at the output

**Answer. 1**

**Q21. Voltage series feedback results in ……………**

- Increase in both input and output impedances
- Decreases in both input and output impedances
- Increase in input impedance and decreases in output impedance
- Decreases in input impedance and increase in output impedance

**Answer. 3**

**Q22. MOSFET can be used as a …………**

- Current controlled capacitor
- Volatge controlled capacitor
- Current controlled inductor
- Voltage controlled induact

**Answer. 2**

**Q23. A change in the value of the emitter resistance Re in a differential amplifier **

- Affects the difference mode gain Ad
- Affects the common mode gain Ac
- Both 1 and 2
- Does not affect either Ad or Ac

**Answer. 2**

**Q24. The bandwidth of an RF tuned amplifier is dependent on ………..**

- Q-factor of the tuned o/p circuit
- Q-factor of the tuned i/p circuit
- Q-Point
- Q-factor of the o/p and i/p circuits as well as Q-point

**Answer. 1**

**Q25. The MOSFET switch in its ON state is equivalent to ……………**

- Resistor
- Inductor
- Capacitor
- Battery

**Answer. 3**

**Q26. Most of the linear ICs are based on the two-transistor differential amplifer because of its ……….**

- Input voltage-dependent linear transfer characteristics
- High voltage gain
- High input resistance
- High CMRR

**Answer. 4**

**Q27. The horizontal intercept of a DC load line is the same as ideal ………….**

- Cut-off point
- Satuaration point
- Operating point
- Quasi-saturation point

**Answer. 1**

**Q28. A differential amplifier is invariably used in the i/p stage of all OP-Amps . This is done basically to provide the OP-Amps with a very high …………….**

- CMRR
- Slew rate
- Open-loop gain

**Answer. 1**

**Q29. The early effect in a BJT is caused by ………….**

- Fast turn-on
- Fast turn-off
- Large collector-base reverse bias
- Large emitter-base forward bias

**Answer. 3**

**Q30. In a transistor leakage current mainly depends on …………….**

- Doping of base
- size of emitter
- rating of the transistor
- Temperature

**Answer. 4**

**Q31. A source follower using a FET usually has a voltage gain which is ………….**

- Greater than 100
- Slightly less than 1 but positive
- Exactly unity but negative
- About -10

**Answer. 1**

**Q32. In an OP-amp differentiator**

- The amplitude of output is proportional to rate of change of input
- The amplitude of output is proportional to input
- Output occurs when input is finite and constant
- Polarity of input and output is the same

**Answer. 1**

**Q34. Class AB operation is often used in power large signal amplifies in order to ……………..**

- Get maximum efficiency
- Remove even harmonics
- Overcome a crossover distortion
- Reducing collector dissipation

**Answer : 3**

**Q35**.** Which of the following amplifier circuit using junction transistor has the best gain?**

- Common base
- Common emitter
- Common collector
- All have the same gain

**Answer: 2**

**Q36. When a transistor is connected in common emitter mode, it will have …………………**

- Negligible input resistance and high output resistance
- High input resistance and low output resistance
- Medium input resistance and high output resistance
- Low input resistance as well as output resistance

**Answer. 3**

**Q37. In all base driver amplifiers, …………………..**

- ac collector voltage is 180
^{0}out of phase with ac base - ac emitter voltage is 180
^{0}out of phase with ac base voltage - ac collector voltage is in phase with ac base voltage
- none of the above

**Answer. 1**

**Q38. The effective channel length of a MOSFET in saturation, decreases with increase in ………………**

- Gate voltage
- Drain voltage
- Source voltage
- Body voltage

**Answer. 2**

**Q39. Which of the following statement is not true?**

- Push-pull signals are equal and opposite in phase
- class AB operation cannot be used for a push-pull audio power output phase
- A push-pull output transformer has a center-tapped primary
- All of the above

**Answer. 2**

**Q40. The encapsulation of a transistor is necessary for ……….**

- Preventing radio interference
- Preventing photo-emission effect
- Avoiding loss of free electrons
- Mechanical ruggedness

**Answer. 4**

**Q41. In deriving ac equivalent circuit for an amplifier circuit we short circuit ………….**

- all transistor
- all resistor
- all inductors
- all capacitors

**Answer. 4**

**Q42. Thermal runaway is not possible in FET because as the temperature of FET increases,……………**

- the mobility decreases
- the transconductance increases
- the drain current increases
- none of the above

**Answer. 1**