TRANSISTORS AND SPECIAL DIODES

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• Q1: What is a Transistor?
  Ans: A transistor is a semiconductor device used to amplify or switch electronic signals.
• Q2: State the uses of Transistors.
  Ans: Uses of transistors are:

  • ➔ Used as an amplifier
  • ➔ Used as a switch
  • ➔ Used in electronic circuits
  • ➔ Used in communication systems
• Q3: What is a Bipolar Junction Transistor?
  Ans: A Bipolar Junction Transistor (BJT) is a transistor that uses both electrons and holes as charge carriers.
• Q4: State the types of Bipolar Junction Transistors.
  Ans: Types of BJT are:

  • ➔ PNP Transistor
  • ➔ NPN Transistor
• Q5: What is a PNP Transistor?
  Ans: A PNP transistor is a type of transistor in which a layer of N-type material is sandwiched between two P-type materials.
• Q6: What is a NPN Transistor?
  Ans: An NPN transistor is a type of transistor in which a layer of P-type material is sandwiched between two N-type materials.
• Q7: Define Emitter.
  Ans: The emitter is the terminal of a transistor that emits charge carriers (electrons or holes).
• Q8: Define Base.
  Ans: The base is the middle terminal of a transistor that controls the flow of charge carriers.
• Q9: Define Collector.
  Ans: The collector is the terminal of a transistor that collects charge carriers.
• Q10: Briefly explain the working of a Transistor.
  Ans: In a transistor, a small current at the base controls a larger current flowing from emitter to collector.
  Thus, it can amplify signals.
• Q11: What is the working principle of a Transistor?
  Ans: The working principle of a transistor is based on the control of current flow by charge carriers through a semiconductor material.
• Q12: Define Transistor Currents.
  Ans: Transistor currents are the currents flowing through its terminals: emitter current (I_E), base current (I_B), and collector current (I_C).
• Q13: Define Transistor Gains. Write the formula.
  Ans: Transistor gain is the ratio of output to input signal.
  General formula:
  
  Gain = Output / Input
• Q14: Define Current Gain. Write the formula.
  Ans: Current gain is the ratio of collector current to base current.
  
  β = I_C / I_B
• Q15: Define Voltage Gain. Write the formula.
  Ans: Voltage gain is the ratio of output voltage to input voltage.
  
  A_v = V_out / V_in
• Q16: Define Power Gain. Write the formula.
  Ans: Power gain is the ratio of output power to input power.
  
  A_p = P_out / P_in
• Q17: What is a BJT Transistor?
  Ans: A BJT transistor is another name for Bipolar Junction Transistor which uses both types of charge carriers.
• Q18: State the terminals of BJT transistors.
  Ans: Terminals of BJT are:

  • ➔ Emitter
  • ➔ Base
  • ➔ Collector
• Q19: State the uses of BJT as an Amplifier.
  Ans: Uses of BJT as amplifier are:

  • ➔ Audio amplification
  • ➔ Signal amplification
  • ➔ Radio and TV circuits
  • ➔ Communication systems
• Q20: Define Common Emitter Amplifier.
  Ans: A common emitter amplifier is a transistor amplifier in which the emitter terminal is common to both input and output.
• Q21: Define Common Base Amplifier.
  Ans: A common base amplifier is a transistor amplifier in which the base terminal is common to both input and output.
• Q22: Define Common Collector Amplifier.
  Ans: A common collector amplifier is a transistor amplifier in which the collector terminal is common to both input and output.
• Q23: Define Zener Diode.
  Ans: A Zener diode is a special type of diode that allows current to flow in reverse direction when a certain voltage is reached.
• Q24: What is Zener Biasing?
  Ans: Zener biasing is the process of operating a Zener diode in reverse bias to maintain a constant voltage.
• Q25: What is the rating of Zener Diode?
  Ans: The rating of a Zener diode is defined by its Zener voltage and power dissipation capacity.
• Q26: Explain Zener Diode as a Shunt Regulator.
  Ans: In a shunt regulator, the Zener diode is connected parallel to the load.
  It maintains constant voltage by allowing excess current to pass through it.
• Q27: What is a Photo Diode?
  Ans: A photodiode is a semiconductor device that converts light into electrical current.
• Q28: State the uses of Photo Diode.
  Ans: Uses of photodiode are:

  • ➔ Light detection
  • ➔ Solar energy systems
  • ➔ Optical communication
  • ➔ Light sensors
• Q29: What is a Solar Cell or a Photo Voltaic Cell?
  Ans: A solar cell is a device that converts sunlight directly into electrical energy.
• Q30: State the working principle of a Solar Cell.
  Ans: A solar cell works on the photovoltaic effect, where light energy is converted into electrical energy.
• Q31: Briefly explain the construction and working of a Solar Cell.
  Ans: A solar cell is made of a PN junction semiconductor.
  When sunlight falls on it, electrons are excited and create current.
  This current is collected and used as electrical energy.
• Q32: Define LED.
  Ans: LED (Light Emitting Diode) is a semiconductor device that emits light when current flows through it.
• Q33: What is Biasing of LEDs?
  Ans: Biasing of LEDs means applying proper forward voltage so that the LED emits light safely.
• Q34: State the uses of LEDs.
  Ans: Uses of LEDs are:

  • ➔ Indicator lights
  • ➔ Display panels
  • ➔ Lighting systems
  • ➔ Electronic devices
• Q35: Define Dark Current.
  Ans: Dark current is the small current that flows in a photodiode even when no light is present.