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câu hỏi |
câu trả lời |
What is static resistance? bắt đầu học
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It is the resistance calculated using Ohm's law as the slope of the V-I curve from the origin to a working point.
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What is dynamic resistance? bắt đầu học
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It is the small-signal resistance calculated from the change in voltage over the change in current (ΔV/ΔI) at a specific point.
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How does temperature affect a standard resistor? bắt đầu học
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Resistance increases with temperature due to its positive thermal coefficient.
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What is a varistor used for? bắt đầu học
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To protect circuits from overvoltage by decreasing resistance sharply above a threshold.
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What does a strain gauge measure? bắt đầu học
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Mechanical strain, by detecting resistance changes when a conductor is stretched.
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How does a thermistor respond to temperature? bắt đầu học
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Its resistance changes with temperature: NTC decreases resistance, PTC increases it.
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What is the function of a photoresistor? bắt đầu học
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To measure light intensity; resistance decreases as light exposure increases.
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State Kirchhoff's Current Law (KCL). bắt đầu học
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The total current entering a node equals the total current leaving it.
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State Kirchhoff's Voltage Law (KVL). bắt đầu học
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The sum of voltages around any closed loop equals zero.
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How does a capacitor behave with frequency? bắt đầu học
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In AC, impedance decreases with frequency; in DC, it acts like an open circuit.
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Define capacitive reactance. bắt đầu học
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Xc = 1 / (2πfC); it measures how a capacitor resists AC.
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What affects capacitance? bắt đầu học
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Plate area, distance between plates, and dielectric constant of material.
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How does an inductor store energy? bắt đầu học
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In a magnetic field created by current flowing through it.
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Define inductive reactance. bắt đầu học
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XL = 2πfL; it increases with frequency, impeding AC.
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bắt đầu học
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Voltage across a conductor due to a magnetic field acting on moving charges.
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What is semiconductor doping? bắt đầu học
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Introducing impurities to create free carriers in a semiconductor.
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How is an N-type semiconductor formed? bắt đầu học
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By adding atoms with more valence electrons, providing free electrons.
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How is a P-type semiconductor formed? bắt đầu học
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By adding atoms with fewer valence electrons, creating holes.
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What is the depletion layer? bắt đầu học
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A non-conductive region at a PN junction where charge carriers cancel out.
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What is forward bias in a diode? bắt đầu học
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Positive voltage on the anode reduces the depletion layer, allowing current.
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What is reverse bias in a diode? bắt đầu học
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Voltage increases the depletion layer, blocking current flow.
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What is the typical forward voltage for a silicon diode? bắt đầu học
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What is a Zener diode used for? bắt đầu học
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Voltage regulation in reverse breakdown mode.
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Why use a Schottky diode? bắt đầu học
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It has a low forward voltage drop and fast switching speed.
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What does β represent in BJTs? bắt đầu học
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The current gain (Ic/Ib).
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What does α represent in BJTs? bắt đầu học
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The ratio of collector current to emitter current (Ic/Ie).
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What is the Q-point in a transistor? bắt đầu học
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The operating point under DC conditions without an input signal.
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How does a JFET control current? bắt đầu học
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By adjusting gate voltage to control the channel width via the depletion layer.
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What is pinch-off voltage in a JFET? bắt đầu học
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The voltage at which drain current levels off and saturates.
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What is an enhancement-mode MOSFET? bắt đầu học
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A transistor that is normally off and requires a positive gate voltage to conduct.
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What is a depletion-mode MOSFET? bắt đầu học
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A transistor that is normally on and turns off with negative gate voltage.
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bắt đầu học
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A circuit that converts AC to DC using diodes.
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bắt đầu học
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A measure of residual AC in the DC output of a rectifier.
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How does a Zener voltage stabilizer work? bắt đầu học
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It maintains a constant output voltage by operating in reverse breakdown.
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What is a current mirror? bắt đầu học
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A circuit that duplicates current from one active device to another.
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What is Total Harmonic Distortion (THD)? bắt đầu học
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A measure of distortion caused by harmonics in an amplifier's output.
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What is Common Mode Rejection Ratio (CMRR)? bắt đầu học
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The ability of an amplifier to reject common input signals.
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What is amplifier slew rate? bắt đầu học
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The maximum rate of change of output voltage in response to a step input.
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What is Signal-to-Noise Ratio (SNR)? bắt đầu học
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The ratio of signal power to noise power, typically in decibels (dB).
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What defines a Class A amplifier? bắt đầu học
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Continuous conduction for the full cycle, with high linearity and low efficiency.
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What defines a Class B amplifier? bắt đầu học
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Each transistor conducts for half the cycle (180°); more efficient, but causes crossover distortion.
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What defines a Class AB amplifier? bắt đầu học
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Conducts slightly more than 180° to eliminate crossover distortion.
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What defines a Class D amplifier? bắt đầu học
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Uses PWM and switching transistors for high efficiency.
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What is an op-amp buffer used for? bắt đầu học
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Signal isolation with high input and low output impedance.
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What does a Schmitt trigger do? bắt đầu học
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Converts noisy signals into clean transitions using hysteresis.
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What is a differential amplifier? bắt đầu học
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Amplifies the difference between two signals while rejecting common noise.
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What is an integrating amplifier? bắt đầu học
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Produces output proportional to the integral of the input voltage over time.
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What is a differentiating amplifier? bắt đầu học
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Produces output proportional to the rate of change of the input voltage.
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What condition is needed for sustained oscillator operation? bắt đầu học
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Unity loop gain (βk = 1) and zero net phase shift (Barkhausen criterion).
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What is the purpose of a DAC (Digital-to-Analog Converter)? bắt đầu học
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To convert digital signals into corresponding analog voltages.
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