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=12πRCf_c = \frac{1}{2\pi RC}fc=2πRC1, 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.