EDC MODEL QUESTION PAPER 20 MARKS MCQ TEST
ATTEND THE TEST GET YOUR SCORES IMMEDIATELY
ECE - EDC - DOTE MODEL QUESTION WITH ANSWERS
- Which circuit converts AC
into DC?
a) Amplifier
b) Rectifier
c) Oscillator
d) Filter
- A circuit that removes a
portion of input signal is called:
a) Clipper
b) Clamper
c) Amplifier
d) Rectifier
- Which device emits light
when forward biased?
a) LED
b) Photo Diode
c) Zener Diode
d) SCR
- Clamper circuit is used to:
a) Shift DC level
b) Clip signal
c) Amplify signal
d) Rectify AC
- In NPN transistor, the
majority carriers are:
a) Holes
b) Electrons
c) Protons
d) Ions
- The transistor region used for amplification is:
a) Active
b) Saturation
c) Cut-off
d) Breakdown
- Voltage divider bias
provides:
a) High stability
b) Poor stability
c) No bias
d) Negative bias
- Which transistor
configuration has highest current gain?
a) CE
b) CB
c) CC
d) None
- A transistor acts as an
amplifier in which region?
a) Active
b) Cut-off
c) Saturation
d) Breakdown
- The amplifier used for
impedance matching is:
a) CC (Common Collector)
b) CE
c) CB
d) Differential
- Which amplifier gives higher
efficiency?
a) Class A
b) Class B
c) Class C
d) Class D
- Differential amplifier
improves:
a) CMRR
b) Gain
c) Noise
d) Power output
- Negative feedback in
amplifier results in:
a) Reduced distortion
b) Increased distortion
c) Increased gain
d) Instability
- Positive feedback is essential
for:
a) Oscillator
b) Amplifier
c) Rectifier
d) Clipper
- Condition for sustained
oscillation is:
a) Barkhausen Criterion
b) Ohm’s Law
c) KCL
d) Norton Theorem
- Hartley oscillator uses:
a) Two inductors
b) Two capacitors
c) RC network
d) Crystal
- FET is a:
a) Unipolar device
b) Bipolar device
c) Thermal device
d) Photonic device
- In JFET, current flows from:
a) Source to Drain
b) Drain to Source
c) Gate to Source
d) Source to Gate
- MOSFET operates in:
a) Enhancement and Depletion modes
b) Reverse mode only
c) Forward mode only
d) Breakdown mode
- UJT is mainly used as:
a) Relaxation oscillator
b) Amplifier
c) Rectifier
d) Filter
UNIT 1
🔌 Rectifiers
1. What is the main purpose of a rectifier?
A) To increase voltage
B) To convert DC to AC
C) To convert AC to DC
D) To amplify signals
✅ Answer: C) To convert AC to DC
2. Which of the following uses only one diode?
A) Full-wave rectifier
B) Bridge rectifier
C) Half-wave rectifier
D) None of these
✅ Answer: C) Half-wave rectifier
3. In a full-wave rectifier, the output frequency is:
A) Equal to input
B) Half of input
C) Double the input
D) Zero
✅ Answer: C) Double the input
4. Bridge rectifier uses how many diodes?
A) 2
B) 3
C) 4
D) 6
✅ Answer: C) 4
5. What is the main advantage of a bridge rectifier over a center-tap rectifier?
A) More diodes used
B) Uses transformer
C) Requires no center tap
D) Expensive
✅ Answer: C) Requires no center tap
---
✂️ Clippers and Clampers
6. Which component is essential in a clipper circuit?
A) Diode
B) Capacitor
C) Inductor
D) Transistor
✅ Answer: A) Diode
7. A positive clipper removes the:
A) Positive half of the waveform
B) Negative half of the waveform
C) Both halves
D) Does not remove any part
✅ Answer: A) Positive half of the waveform
8. Which clipper allows current flow in only one direction and clips voltage beyond a specific level?
A) Biased clipper
B) Unbiased clipper
C) Negative clipper
D) Zener clipper
✅ Answer: A) Biased clipper
9. The component responsible for fixing the clamping level in a clamper circuit is:
A) Diode
B) Resistor
C) Capacitor
D) Battery or voltage source
✅ Answer: D) Battery or voltage source
10. What does a positive clamper do to a waveform?
A) Raises it above the zero level
B) Clips the top portion
C) Lowers it below zero level
D) Removes negative half-cycle
✅ Answer: C) Lowers it below zero level
11. Which of the following is not a type of clipper?
A) Positive clipper
B) Negative clipper
C) Series clipper
D) Center clipper
✅ Answer: D) Center clipper
12. Clampers are used to:
A) Change peak voltage
B) Change DC level
C) Clip the signal
D) Amplify input
✅ Answer: B) Change DC level
13. The basic components of a clamper circuit include:
A) Diode and transformer
B) Resistor and capacitor
C) Diode, resistor, and capacitor
D) Inductor and diode
✅ Answer: C) Diode, resistor, and capacitor
---
💡 Opto-Electronic Devices
14. Which diode emits light when forward biased?
A) Zener Diode
B) Photo-Diode
C) LED
D) Tunnel Diode
✅ Answer: C) LED
15. LED stands for:
A) Light Emitting Device
B) Light Emitting Diode
C) Linear Energy Diode
D) Low Energy Display
✅ Answer: B) Light Emitting Diode
16. Photo-diode operates in which biasing condition?
A) Forward bias
B) Reverse bias
C) Zero bias
D) Both
✅ Answer: B) Reverse bias
17. Photo-diode is used to:
A) Emit light
B) Regulate voltage
C) Detect light
D) Store charge
✅ Answer: C) Detect light
18. Which factor affects the intensity of light emitted by an LED?
A) Voltage drop
B) Temperature
C) Reverse current
D) Forward current
✅ Answer: D) Forward current
19. Which device generates current when exposed to light?
A) LED
B) Zener diode
C) Photo-diode
D) Varactor diode
✅ Answer: C) Photo-diode
20. In LED, the color of emitted light depends on:
A) Power supply
B) Current
C) Semiconductor material
D) Size of diode
✅ Answer: C) Semiconductor material
UNIT 2
⚙️ 1. BJT Basics & Working Principle
1. What does BJT stand for?
A) Bipolar Junction Terminal
B) Bipolar Junction Transistor
C) Bi-Junction Terminal
D) Bipolar Jet Transistor
✅ Answer: B) Bipolar Junction Transistor
2. Which of the following is a current-controlled device?
A) FET
B) MOSFET
C) BJT
D) UJT
✅ Answer: C) BJT
3. In an NPN transistor, the majority charge carriers are:
A) Holes
B) Electrons
C) Neutrons
D) Ions
✅ Answer: B) Electrons
4. What is the function of the base region in a BJT?
A) Acts as main current path
B) Controls the current flow
C) Blocks current
D) Stores energy
✅ Answer: B) Controls the current flow
5. In a PNP transistor, current flows from:
A) Collector to emitter
B) Base to collector
C) Emitter to collector
D) Collector to base
✅ Answer: C) Emitter to collector
---
🔄 2. BJT Modes of Operation
6. Which BJT mode is used for amplification?
A) Cut-off
B) Saturation
C) Active
D) Reverse
✅ Answer: C) Active
7. In the cut-off region of a transistor:
A) Base-emitter junction is forward-biased
B) Collector current is maximum
C) Both junctions are reverse-biased
D) Base-collector junction is forward-biased
✅ Answer: C) Both junctions are reverse-biased
8. When a transistor is in saturation:
A) Acts as an amplifier
B) Acts as an insulator
C) Acts as a switch (ON)
D) No current flows
✅ Answer: C) Acts as a switch (ON)
9. In active mode, the base-emitter junction is:
A) Reverse-biased
B) Forward-biased
C) No bias
D) Short-circuited
✅ Answer: B) Forward-biased
10. In which mode does a BJT act as a switch (OFF)?
A) Active
B) Saturation
C) Cut-off
D) Breakdown
✅ Answer: C) Cut-off
---
🧩 3. Transistor Configurations
11. Which transistor configuration gives high voltage gain?
A) Common Collector
B) Common Base
C) Common Emitter
D) All of the above
✅ Answer: C) Common Emitter
12. Which configuration is best for impedance matching?
A) Common Emitter
B) Common Base
C) Common Collector
D) None
✅ Answer: C) Common Collector
13. In CB configuration, the input is between:
A) Collector and base
B) Emitter and base
C) Base and emitter
D) Collector and emitter
✅ Answer: B) Emitter and base
14. In CE configuration, the output is taken from:
A) Emitter
B) Base
C) Collector
D) Ground
✅ Answer: C) Collector
15. Which configuration has unity current gain?
A) Common Emitter
B) Common Base
C) Common Collector
D) Both B and C
✅ Answer: B) Common Base
---
⚡ 4. Transistor Biasing
16. Why is biasing necessary in a transistor circuit?
A) To turn it off
B) To change resistance
C) To fix the operating point
D) To reduce noise
✅ Answer: C) To fix the operating point
17. The ratio of change in collector current to change in base current is called:
A) Alpha
B) Beta
C) Stability factor
D) Gain
✅ Answer: B) Beta
18. Which biasing method gives best stability?
A) Fixed bias
B) Collector-to-base bias
C) Voltage divider bias
D) Base resistor bias
✅ Answer: C) Voltage divider bias
19. Which of the following biasing circuits requires the least components?
A) Voltage divider
B) Fixed bias
C) Emitter feedback
D) Collector feedback
✅ Answer: B) Fixed bias
20. Stability factor (S) indicates:
A) Temperature resista
nce
B) Gain
C) Output power
D) Sensitivity to IC changes
✅ Answer: D) Sensitivity to IC changes
UNIT 3
🔌 1. Transistor as Amplifier and Switch
1. What does a transistor do in an amplifier circuit?
A) Blocks current
B) Increases signal strength
C) Acts as a filter
D) Stores energy
✅ Answer: B) Increases signal strength
2. When a transistor is used as a switch, in which regions does it operate?
A) Cut-off and Active
B) Active and Saturation
C) Saturation and Cut-off
D) Breakdown and Active
✅ Answer: C) Saturation and Cut-off
3. In the CE amplifier, the input is applied between:
A) Base and Collector
B) Emitter and Collector
C) Base and Emitter
D) Collector and Ground
✅ Answer: C) Base and Emitter
4. Which amplifier configuration offers both voltage and current gain?
A) Common Base
B) Common Collector
C) Common Emitter
D) None
✅ Answer: C) Common Emitter
5. What phase relationship exists between input and output in a CE amplifier?
A) 0°
B) 90°
C) 180°
D) 360°
✅ Answer: C) 180°
---
🎚️ 2. RC Coupled Amplifier
6. RC coupled amplifiers are mainly used for:
A) Power amplification
B) Low-frequency amplification
C) Radio transmission
D) High voltage control
✅ Answer: B) Low-frequency amplification
7. What is the main coupling element between stages in an RC coupled amplifier?
A) Transformer
B) Capacitor
C) Inductor
D) Diode
✅ Answer: B) Capacitor
8. Which is a disadvantage of RC coupled amplifiers?
A) Poor frequency response
B) High cost
C) Low power gain
D) Bulky design
✅ Answer: C) Low power gain
9. What is the bandwidth of an RC coupled amplifier dependent on?
A) Base resistor
B) Coupling capacitor and load
C) Supply voltage
D) Collector resistor
✅ Answer: B) Coupling capacitor and load
10. RC coupled amplifier gives maximum gain in which frequency range?
A) Low
B) Mid
C) High
D) Very high
✅ Answer: B) Mid
---
🔊 3. Power Amplifiers
11. Which class of power amplifier has the highest efficiency?
A) Class A
B) Class B
C) Class C
D) Class AB
✅ Answer: C) Class C
12. Which amplifier has output for the full 360° of the input cycle?
A) Class A
B) Class B
C) Class C
D) Class D
✅ Answer: A) Class A
13. Which power amplifier operates only for 180° of the input signal?
A) Class A
B) Class B
C) Class C
D) Class AB
✅ Answer: B) Class B
14. What is the major drawback of Class B amplifier?
A) Low gain
B) High distortion
C) Cross-over distortion
D) High cost
✅ Answer: C) Cross-over distortion
15. Which amplifier configuration helps eliminate cross-over distortion?
A) Class A
B) Class B
C) Push-pull
D) Cascode
✅ Answer: C) Push-pull
---
🧩 4. Multistage & Special Amplifiers
16. The purpose of using multistage amplifiers is to:
A) Reduce gain
B) Improve stability
C) Increase overall gain
D) Reduce power consumption
✅ Answer: C) Increase overall gain
17. What is a Darlington pair known for?
A) Low gain
B) High current gain
C) High voltage gain
D) Low input impedance
✅ Answer: B) High current gain
18. Cascode amplifier is a combination of:
A) Two CE amplifiers
B) CE and CB amplifiers
C) CB and CC amplifiers
D) CE and CC amplifiers
✅ Answer: B) CE and CB amplifiers
19. In a cascade amplifier, the output of one stage is:
A) Input to the power supply
B) Fed back to the input
C) Input to the next stage
D) Grounded
✅ Answer: C) Input to the next stage
20. CMRR is associated with which amplifier?
A) Class B
B) RC Coupled
C) Differential
D) Power
✅ Answer: C) Differential
UNIT 4
🔁 1. Feedback Amplifiers
1. What is feedback in an amplifier circuit?
A) Adding noise
B) Sending part of the output to input
C) Boosting power supply
D) Disconnecting input
✅ Answer: B) Sending part of the output to input
2. Which of the following is a type of feedback?
A) Linear and Nonlinear
B) Series and Parallel
C) Positive and Negative
D) Direct and Indirect
✅ Answer: C) Positive and Negative
3. What is the effect of negative feedback on bandwidth?
A) Decreases it
B) No effect
C) Increases it
D) Reverses polarity
✅ Answer: C) Increases it
4. Negative feedback in amplifiers improves:
A) Distortion
B) Noise
C) Stability
D) Input voltage
✅ Answer: C) Stability
5. Which type of feedback reduces gain but increases linearity?
A) Positive
B) Negative
C) Regenerative
D) Capacitive
✅ Answer: B) Negative
6. The four types of negative feedback amplifiers are based on:
A) Current and voltage feedback
B) Biasing methods
C) Resistor values
D) Capacitance type
✅ Answer: A) Current and voltage feedback
7. Negative feedback reduces:
A) Input resistance
B) Output resistance
C) Bandwidth
D) Distortion
✅ Answer: D) Distortion
8. In a voltage series feedback amplifier, the feedback is taken from:
A) Output current
B) Input voltage
C) Output voltage
D) Input current
✅ Answer: C) Output voltage
---
🌀 2. Theory of Oscillation
9. Which circuit stores energy in both inductor and capacitor?
A) Amplifier
B) Tank Circuit
C) Filter
D) Transformer
✅ Answer: B) Tank Circuit
10. Which is a basic condition for oscillation?
A) Zero gain
B) Infinite feedback
C) Barkhausen criterion
D) No input
✅ Answer: C) Barkhausen criterion
11. The Barkhausen criterion requires:
A) Loop gain = 0
B) Loop gain > 1
C) Loop gain = 1 with 0° phase shift
D) Output voltage = 0
✅ Answer: C) Loop gain = 1 with 0° phase shift
12. Oscillators are classified based on:
A) Frequency range
B) Phase difference
C) Feedback used
D) Type of wave generated
✅ Answer: C) Feedback used
---
🔊 3. Oscillator Circuits
13. Which oscillator uses a tapped inductor for frequency determination?
A) Colpitts
B) Hartley
C) Wien Bridge
D) Crystal
✅ Answer: B) Hartley
14. In a Colpitts oscillator, feedback is derived from:
A) Resistors
B) Inductors
C) Capacitor voltage divider
D) Transformer
✅ Answer: C) Capacitor voltage divider
15. The RC Phase Shift Oscillator uses how many RC sections?
A) 1
B) 2
C) 3
D) 4
✅ Answer: C) 3
16. Wien bridge oscillator is commonly used to generate:
A) Sawtooth wave
B) Sine wave
C) Square wave
D) Triangular wave
✅ Answer: B) Sine wave
17. Which component provides stability in a Crystal Oscillator?
A) Capacitor
B) Inductor
C) Resistor
D) Quartz crystal
✅ Answer: D) Quartz crystal
18. Hartley oscillator uses which components to determine frequency?
A) R and C
B) L and C
C) Only R
D) Only C
✅ Answer: B) L and C
19. Which oscillator is most stable in frequency?
A) Hartley
B) RC Phase Shift
C) Wien Bridge
D) Crystal
✅ Answer: D) Crystal
20. Oscillator circuits generate output without:
A) Power supply
B) Input signal
C) Gr
ound connection
D) Feedback
✅ Answer: B) Input signal
UNIT 5
🔷 1. FET Basics
-
What does FET stand for?
A) Field Emission Transistor
B) Field Energy Transistor
C) Field Effect Transistor
D) Fixed Electron Transistor
✅ Answer: C) Field Effect Transistor -
FETs are classified into:
A) BJT and JFET
B) JFET and MOSFET
C) UJT and BJT
D) SCR and TRIAC
✅ Answer: B) JFET and MOSFET -
The input impedance of FET is:
A) Very low
B) Moderate
C) High
D) Zero
✅ Answer: C) High -
FET is controlled by:
A) Current
B) Voltage
C) Power
D) Resistance
✅ Answer: B) Voltage -
Which terminal controls the flow of current in JFET?
A) Drain
B) Source
C) Gate
D) Body
✅ Answer: C) Gate
🧿 2. JFET – Junction Field Effect Transistor
-
In N-channel JFET, the majority carriers are:
A) Holes
B) Electrons
C) Protons
D) Neutrons
✅ Answer: B) Electrons -
The characteristic curve of JFET is called:
A) Load line
B) Transfer curve
C) Output curve
D) Saturation curve
✅ Answer: B) Transfer curve -
The region where JFET operates as a constant current source is:
A) Cut-off
B) Ohmic
C) Active
D) Saturation
✅ Answer: D) Saturation -
Pinch-off voltage in a JFET is the voltage at which:
A) The current becomes zero
B) Gate current starts flowing
C) Channel is fully open
D) Current becomes constant
✅ Answer: D) Current becomes constant -
JFET has how many terminals?
A) 2
B) 3
C) 4
D) 5
✅ Answer: B) 3
⚙️ 3. MOSFET – Metal Oxide Semiconductor FET
-
MOSFET has how many operating modes?
A) 2
B) 3
C) 4
D) 5
✅ Answer: A) 2 (Enhancement and Depletion) -
In N-channel Enhancement mode MOSFET, the channel is formed:
A) At zero gate voltage
B) By forward biasing gate
C) When V_GS exceeds threshold
D) At negative voltage
✅ Answer: C) When V_GS exceeds threshold -
The key difference between JFET and MOSFET is:
A) Gate is insulated in MOSFET
B) MOSFET has lower gain
C) JFET uses holes as carriers
D) JFET is faster
✅ Answer: A) Gate is insulated in MOSFET -
The substrate terminal in a MOSFET is also known as:
A) Base
B) Drain
C) Body
D) Channel
✅ Answer: C) Body -
Which MOSFET can operate with both positive and negative gate voltage?
A) Depletion-mode
B) Enhancement-mode
C) BJT
D) IGBT
✅ Answer: A) Depletion-mode
🌀 4. UJT – Uni Junction Transistor
-
How many junctions does a UJT have?
A) 1
B) 2
C) 3
D) 4
✅ Answer: A) 1 -
The UJT is mainly used as a:
A) Amplifier
B) Comparator
C) Oscillator
D) Switch
✅ Answer: C) Oscillator -
UJT has how many terminals?
A) 2
B) 3
C) 4
D) 5
✅ Answer: B) 3 (Emitter, Base1, Base2) -
The UJT relaxation oscillator produces which waveform?
A) Sinusoidal
B) Triangular
C) Sawtooth
D) Square
✅ Answer: C) Sawtooth -
The UJT is a:
A) Voltage-controlled device
B) Current-controlled device
C) Temperature-controlled
D) Resistance-controlled
✅ Answer: A) Voltage-controlled device
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