FETs are unipolar devices because their operation depends only on one type of charge carrier (either electrons or holes). In contrast, BJTs are bipolar devices as they involve both electrons and holes for their operation.
What is the primary function of a diode?
A To amplify signals
B To allow current flow in one direction only
C To store energy
D To act as a frequency filter
A diode is a semiconductor device that permits current to flow in one direction (forward-biased) and blocks it in the reverse direction (reverse-biased). This property makes it useful in rectifiers and other circuits.
What is the voltage drop across an ideal diode in forward bias?
A 0 V
B 0.3 V
C 0.7 V
D 1 V
In an ideal diode, the voltage drop in forward bias is zero. However, in practical silicon diodes, it is around 0.7 V, and in germanium diodes, it is about 0.3 V.
Which of the following is NOT a type of rectifier?
A Half-wave rectifier
B Full-wave rectifier
C Bridge rectifier
D Amplifier
Rectifiers are used to convert AC to DC. The types include half-wave, full-wave, and bridge rectifiers. Amplifiers, on the other hand, are used to increase the amplitude of a signal.
In an NPN transistor, the majority charge carriers in the base are:
A Electrons
B Holes
C Both electrons and holes
D None of the above
In an NPN transistor, the base is a P-type material. Therefore, holes are the majority carriers in the base, whereas electrons are the minority carriers.
Which of the following configurations provides the highest voltage gain in BJTs?
A Common Base
B Common Emitter
C Common Collector
D Darlington Pair
The common-emitter configuration provides high voltage and current gain, making it ideal for amplification. Common base offers high voltage gain but low current gain, and common collector offers high current gain but low voltage gain.
What is the input impedance of a common base configuration in BJTs?
A High
B Medium
C Low
D Zero
The common base configuration has low input impedance because the base-emitter junction is forward-biased, resulting in a low resistance path for the input signal.
What is the purpose of a bypass capacitor in an amplifier circuit?
A To increase DC voltage
B To improve the frequency response
C To stabilize the AC signal
D To block DC and allow AC signals
A bypass capacitor is used to short-circuit AC signals to ground, allowing only DC signals to pass through in the circuit. It helps stabilize the output.
Which of the following is a characteristic of an ideal op-amp?
A Infinite gain
B Zero input impedance
C Low output impedance
D Both A and C
An ideal op-amp has infinite voltage gain, infinite input impedance (to prevent loading), and zero output impedance (to deliver maximum current to the load).
In a class A amplifier, the Q-point is located:
A At cutoff
B At saturation
C In the middle of the load line
D At the origin
The Q-point in a Class A amplifier is positioned in the middle of the load line to allow maximum undistorted signal swing.
What is the function of negative feedback in amplifiers?
A To increase gain
B To improve stability
C To decrease bandwidth
D To increase distortion
Negative feedback improves the stability of an amplifier by reducing gain and distortion, increasing bandwidth, and making the system more linear.
Which device is used to convert an analog signal to a digital signal?
A DAC
B ADC
C Op-amp
D Oscillator
An Analog-to-Digital Converter (ADC) converts analog signals into digital signals for processing by digital systems.
What is the primary function of a voltage regulator?
A To amplify voltage
B To filter AC signals
C To provide a stable DC voltage
D To convert DC to AC
Voltage regulators maintain a constant output voltage regardless of changes in input voltage or load conditions.
What is the output impedance of an ideal op-amp?
A Infinite
B Zero
C High
D Variable
An ideal op-amp has zero output impedance, ensuring maximum power transfer to the load without any voltage drop.
What is the purpose of a Zener diode in voltage regulation?
A To conduct only in one direction
B To block current flow
C To maintain a constant voltage
D To amplify signals
Zener diodes are used in voltage regulation circuits to maintain a stable output voltage by allowing current to flow in the reverse breakdown region, providing a constant voltage drop.
Which component is used to convert AC to DC?
A Resistor
B Inductor
C Rectifier
D Transformer
Rectifiers are electronic circuits that convert alternating current (AC) into direct current (DC). Common examples are half-wave and full-wave rectifiers.
What is the forward voltage drop of a silicon diode in its conducting state?
A 0.3 V
B 0.7 V
C 1.1 V
D 0 V
Silicon diodes have a typical forward voltage drop of 0.7 V when conducting. For germanium diodes, this is around 0.3 V.
What is the unit of capacitance?
A Ohm
B Farad
C Henry
D Coulomb
Capacitance is measured in farads (F) and represents the ability of a component to store charge.
What is the primary purpose of an inductor in analog circuits?
A To store energy in a magnetic field
B To amplify signals
C To store energy in an electric field
D To convert DC to AC
Inductors store energy in their magnetic field when current flows through them and are commonly used in filters and oscillators.
What does the term โgainโ in amplifiers refer to?
A Power loss
B Voltage or current increase
C Resistance reduction
D Signal filtering
Gain is the ratio of output signal amplitude to input signal amplitude in an amplifier. It can be expressed as voltage gain, current gain, or power gain.
Which type of amplifier operates only for less than 180 degrees of the input signal cycle?
A Class A
B Class B
C Class C
D Class AB
Class C amplifiers are biased such that they conduct for less than half of the input signal cycle, making them suitable for high-frequency applications like RF transmitters.
What does a transistor act as in a switching circuit?
A A resistor
B A capacitor
C A switch
D A voltage source
Transistors act as switches by turning on (conducting) or off (non-conducting) states depending on the applied input signal.
Which part of a transistor controls the flow of current?
A Collector
B Base
C Emitter
D None of the above
In a transistor, the base acts as a control terminal, allowing or restricting current flow between the collector and emitter.
What is the function of a capacitor in a filter circuit?
A To block DC while allowing AC
B To amplify signals
C To reduce current
D To store magnetic energy
Capacitors in filter circuits block DC components while allowing AC signals to pass, making them essential in signal conditioning.
Which amplifier configuration is known for providing high input impedance?
A Common Collector
B Common Emitter
C Common Base
D Push-Pull
The common collector configuration (emitter follower) has high input impedance and is used for impedance matching.
In an operational amplifier, what is the ideal value of the input offset voltage?
A Zero
B Infinite
C Negative
D Positive
The ideal input offset voltage of an op-amp is zero, meaning no input voltage is needed to make the output zero.
What determines the frequency of oscillation in an RC oscillator?
A Resistance only
B Capacitance only
C Both resistance and capacitance
D None of the above
In an RC oscillator, the frequency of oscillation is determined by the values of the resistors and capacitors in the circuit.
Which type of rectifier uses four diodes in its circuit?
A Half-wave rectifier
B Full-wave rectifier
C Bridge rectifier
D Voltage multiplier
A bridge rectifier uses four diodes arranged in a bridge configuration to convert AC to DC efficiently.
What is the role of feedback in an oscillator circuit?
A To amplify noise
B To stabilize DC voltage
C To sustain oscillations
D To block signals
Positive feedback in an oscillator circuit feeds a portion of the output back to the input to sustain oscillations.
What is the bandwidth of an amplifier?
A The range of frequencies it can amplify
B The range of voltages it can handle
C The maximum gain it can provide
D The input impedance
Bandwidth refers to the range of frequencies over which an amplifier operates effectively without significant loss in gain.
Which of the following is a bilateral device?
A Diode
B Transistor
C Resistor
D SCR (Silicon Controlled Rectifier)
A bilateral device conducts current equally well in both directions. Resistors are bilateral, whereas diodes and SCRs are unidirectional devices.
What does a small-signal model of a transistor represent?
A Nonlinear behavior
B High-frequency operation
C Linearized behavior around a bias point
D Switching characteristics
Small-signal models linearize the transistor’s nonlinear behavior near the operating point for easier analysis of small AC signals.
What is the main disadvantage of a class B amplifier?
A High distortion
B Low efficiency
C High power consumption
D Limited bandwidth
Class B amplifiers exhibit crossover distortion because the two halves of the signal are amplified by different transistors, creating gaps around the zero-crossing point.
What is the output of a differentiator circuit when the input is a ramp signal?
A A constant
B A sine wave
C An exponential signal
D A square wave
A differentiator circuit calculates the derivative of the input. For a ramp input (linear increase), the output is a constant value corresponding to the slope of the ramp.
Which type of feedback improves the stability of an amplifier?
A Positive feedback
B Negative feedback
C Current feedback
D Voltage feedback
Negative feedback reduces the gain but improves stability, linearity, and bandwidth while minimizing distortion and noise.
Which of the following statements is true for an ideal op-amp?
A It has infinite bandwidth
B It has zero input impedance
C It has finite output impedance
D It requires large input current
An ideal op-amp is assumed to have infinite bandwidth, infinite input impedance, and zero output impedance, making it perfect for amplification without losses.
Which transistor region is used for amplification in BJTs?
A Cutoff region
B Saturation region
C Active region
D Breakdown region
In the active region, the transistor’s base-emitter junction is forward-biased, and the collector-base junction is reverse-biased, enabling linear amplification.
Which parameter is used to measure the noise performance of an amplifier?
A Gain
B Bandwidth
C Noise figure
D Slew rate
The noise figure quantifies how much noise an amplifier adds to the input signal, critical for sensitive signal applications.
What type of rectifier provides the highest efficiency?
A Half-wave rectifier
B Full-wave rectifier
C Bridge rectifier
D Voltage doubler
Full-wave rectifiers have an efficiency of 81.2%, higher than half-wave rectifiers (40.6%) because they utilize both halves of the AC cycle.
What is the main purpose of a current mirror circuit?
A To amplify current
B To stabilize voltage
C To copy current from one branch to another
D To filter noise
A current mirror replicates a current flowing in one branch of a circuit in another branch, commonly used in ICs for biasing.
What is the effect of thermal runaway in a transistor?
A Increased efficiency
B Constant current flow
C Device failure due to overheating
D Reduced gain
Thermal runaway occurs when increased current flow causes excessive heating, which further increases current, leading to transistor failure.
What is the primary purpose of a bypass capacitor in an emitter follower circuit?
A To block AC signals
B To stabilize DC bias
C To increase input impedance
D To reduce voltage gain
A bypass capacitor prevents AC signals from affecting the DC bias by providing a low-impedance path to ground for AC signals.
Which type of MOSFET is normally ON in the absence of a gate signal?
A Enhancement-mode MOSFET
B Depletion-mode MOSFET
C N-channel MOSFET
D P-channel MOSFET
Depletion-mode MOSFETs are normally ON without a gate signal, while enhancement-mode MOSFETs require a positive gate voltage to conduct.
What determines the cut-off frequency in a low-pass RC filter?
A Resistance only
B Capacitance only
C Both resistance and capacitance
D Inductance
The cut-off frequency of a low-pass RC filter is calculated as fc=12ฯRCf_c = \frac{1}{2\pi RC}fc=2ฯRC1, dependent on both resistance and capacitance.
What does the gain-bandwidth product (GBP) represent?
A The product of voltage and current gain
B The trade-off between gain and bandwidth
C The maximum output power
D The noise level
The gain-bandwidth product indicates that as the gain of an amplifier increases, the bandwidth decreases, and vice versa.
What is the primary function of an operational amplifier in a circuit?
A Voltage regulation
B Signal amplification
C Current rectification
D Frequency generation
An operational amplifier (op-amp) is a high-gain electronic voltage amplifier used to amplify weak input signals in various configurations, including inverting, non-inverting, and differential modes.
Which component is used to block DC and pass AC in a circuit?
A Diode
B Capacitor
C Resistor
D Inductor
Capacitors block DC while allowing AC signals to pass through due to their frequency-dependent reactance.
What type of transistor configuration provides the highest current gain?
A Common Base
B Common Emitter
C Common Collector
D Darlington Pair
A Darlington pair consists of two transistors connected in such a way that the overall current gain is the product of the gains of the two transistors, making it significantly higher than other configurations.
What happens to the resistance of a semiconductor when temperature increases?
A Increases
B Decreases
C Remains constant
D Becomes infinite
In semiconductors, increasing temperature excites more electrons to the conduction band, decreasing resistance as conductivity improves.
What type of filter is used in a tuning circuit to select a specific frequency?
A Low-pass filter
B High-pass filter
C Band-pass filter
D Band-stop filter
A band-pass filter allows a specific range of frequencies to pass through while attenuating frequencies outside this range, making it ideal for tuning circuits.