Ch 3: Diodes and Transistors Flashcards
Q: What is a diode?
A: A semiconductor device that allows current to flow in one direction only.
Q: Define the forward bias of a diode.
A: A condition where the positive terminal of the voltage source is connected to the anode of the diode.
Q: What is reverse bias in a diode?
A: A condition where the positive terminal is connected to the cathode, blocking current flow.
Q: What is the function of a Zener diode?
A: To regulate voltage by allowing current to flow in reverse when a specific breakdown voltage is reached.
Q: What is a light-emitting diode (LED)?
A: A diode that emits light when forward-biased.
Q: What is a transistor?
A: A semiconductor device used to amplify or switch electronic signals.
Q: Name the three terminals of a bipolar junction transistor (BJT).
A: Emitter, base, and collector.
Q: What is the difference between NPN and PNP transistors?
A: In NPN, current flows from collector to emitter; in PNP, it flows from emitter to collector.
Q: What is the function of an operational amplifier (op-amp)?
A: To amplify input signals with high gain.
Q: How does a photodiode work?
A: It converts light into electrical current.
Q: What is the threshold voltage (barrier voltage) of a diode?
A: The minimum voltage required to make the diode conduct in forward bias.
Q: What is a field-effect transistor (FET)?
A: A transistor controlled by electric field to regulate current flow.
Q: Define the saturation region of a transistor.
A: A region where the transistor is fully on and conducts maximum current.
Q: What is a logic gate?
A: A digital circuit that performs logical operations.
Q: What is a MOSFET?
A: Metal-Oxide-Semiconductor Field-Effect Transistor, widely used in electronic devices.
Q: How is a diode used in rectification?
A: To convert AC to DC by allowing current in one direction.
Q: What is a Schottky diode?
A: A diode with low forward voltage drop and fast switching.
Q: What is a transistor’s cutoff region?
A: The state where the transistor is off and no current flows.
Q: What is a current amplifier?
A: A circuit using transistors to increase current.
Q: What is the power dissipation of a diode?
A: The heat produced due to voltage drop and current refers to the amount of electrical power converted into heat as current flows through the diode.
Q: What is the depletion region in a diode?
A: The area where no charge carriers are present due to recombination.
Q: How does a transistor act as a switch?
A: By toggling between cutoff and saturation regions.
Q: What is a phototransistor?
A: A transistor that is sensitive to light and amplifies the signal.
Q: What is the main application of a Zener diode?
A: Voltage regulation.
Q: What is the use of a transistor in amplifiers?
A: To increase the amplitude of input signals.
Q: Why does an incandescent light bulb remain off when connected to a Zener diode voltage regulator with Vin = 6 V and Vzener = 5 V?
A: The Zener diode is reverse-biased, causing all currents to flow through it and no current through the light bulb.
Q: What makes Zener diodes superior to thermistors in signal linearity?
A: Zener diodes show linear response to temperature changes, unlike thermistors.
Q: What happens to the output voltage of a Zener diode with power supply fluctuations?
A: It remains stable within its operational range, unlike thermistors.
Q: What is the Zener voltage of an LM335 sensor at 300 K?
A: +3.00 V.
Q: What causes an LM335 Zener diode to output higher-than-expected voltages?
A: Self-heating due to excessive input current.