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Transistor As a Switch and Amplifier
A transistor can switch between low- and high-conduction states or amplify signals. Output energy comes from the external supply, not from the transistor itself.
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Transistor As a Switch and Amplifier
A transistor can work like a switch controlled by a tiny signal.
It can also make a weak signal control a stronger output signal.
Recommended for Class 10
Transistor As a Switch and Amplifier
A transistor has two especially important uses in electronic circuits:
1. Switching
2. Amplification
Transistor as a Switch
A transistor can be operated between states where the collector-emitter path carries very little current and where it conducts strongly.
This makes it useful as an electronic switch.
A small input at the base can therefore control a larger load current.
Transistor as an Amplifier
A small variation in the input signal can control a larger variation in the output circuit.
This is called amplification.
The extra output energy does not come from the transistor itself. It comes from the external power supply.
The transistor controls this energy according to the input signal.
Applications
Switching:
digital circuits; automatic controls; * sensor circuits.
Amplification:
audio circuits; communication equipment; * sensor signals.
Transistor As a Switch and Amplifier — Advanced
In switching applications a transistor is driven between low-conduction and high-conduction operating states. In amplification, operation in an appropriate active region allows small input variations to control larger output variations.
Common Mistakes
Common Mistakes
- Mistake
Mistake: An amplifier creates energy. Correction: The extra output energy comes from the external power supply; the transistor controls it.
Revision Zone
60-Second Revision
Quick cues from this topic — use them for last-minute revision.
Switch → controls ON/OFF states.
Amplifier → small signal controls larger signal.
Energy → external supply.
- Definition
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Practice
PQ
Q1. Explain transistor as switch.
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Q2. Explain transistor as amplifier.
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Q3. Where does amplifier energy come from?
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Q4. Give switching application.
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Q5. Give amplification application.
Exam Practice
EQ
Q1. Explain transistor switching.
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Q2. Explain transistor amplification.
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Q3. Why does amplification not violate conservation of energy?
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Q4. Give applications.
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Q5. Compare switching and amplification.
School-standard facts for Matric and Intermediate. Original explanations — not copied from textbooks.