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Questions and Answers
What is the state of a bipolar junction transistor in the cutoff region?
What is the state of a bipolar junction transistor in the cutoff region?
In an NPN transistor, the flow of current primarily occurs from which terminal to which terminal?
In an NPN transistor, the flow of current primarily occurs from which terminal to which terminal?
What is a disadvantage of bipolar junction transistors?
What is a disadvantage of bipolar junction transistors?
Which mode indicates that a BJT is functioning as a switch in the ON state?
Which mode indicates that a BJT is functioning as a switch in the ON state?
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What is the primary role of the base terminal in a bipolar junction transistor?
What is the primary role of the base terminal in a bipolar junction transistor?
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What is the primary application for bipolar junction transistors in temperature sensing?
What is the primary application for bipolar junction transistors in temperature sensing?
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Why are BJTs infrequently used in integrated circuits?
Why are BJTs infrequently used in integrated circuits?
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Which of the following statements about the forward voltage drop in BJTs is correct?
Which of the following statements about the forward voltage drop in BJTs is correct?
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Study Notes
Bipolar Junction Transistor (BJT)
- A three-terminal semiconductor device consisting of two p-n junctions.
- Terminals:
- Base: Controls the flow of current between emitter and collector.
- Emitter: Source of current in PNP transistors.
- Collector: Source of current in NPN transistors.
Types of BJT
- NPN: Majority charge carrier is an electron; current flow is Collector-Emitter.
- PNP: Majority charge carrier is a Hole; current flow is Emitter-Collector.
BJT Regions of Operation
- Saturation: Both collector-base and emitter-base junctions are forward-biased. This is the ON state of a switch. Maximum current flows between emitter and collector (Ic = Isaturation).
- Cutoff: Both collector-base and emitter-base junctions are reverse-biased. This is the OFF state of a switch. No external supplies are connected, resulting in no collector or emitter current. Achieved by reducing base voltage below both emitter and collector voltage (Vbe < 0.7).
Advantages of BJT
- Large Gain Bandwidth: Difference between maximum and minimum cutoff frequency.
- Low Voltage Drop: 0.6V forward voltage drop.
- Long Life: Various biasing techniques can increase device life.
Disadvantages of BJT
- Low Switching Frequency: Slow switching speed limits use in integrated circuits.
- Leakage Current: Presence of small undesirable currents.
- Low Thermal Stability: Sensitive to temperature fluctuations.
Applications of BJT
- Converters: Used in buck, boost converters, inverters, and various DC-DC, DC-AC, AC-AC, and AC-DC converters.
- Temperature Sensor: Detects temperature by measuring the voltage difference between two levels at a known ratio.
- High Driving Capability: Capable of handling high voltage and current. Devices can be connected in series and parallel to increase capability.
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Description
Test your knowledge on Bipolar Junction Transistors (BJTs), their structure, types, and operating regions. This quiz covers the essential aspects of NPN and PNP transistors and their functionality in electronic circuits.
