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BJT CE Mode Explanation

The document discusses the operation of a Bipolar Junction Transistor (BJT) in Common Emitter (CE) mode, highlighting its configuration, working principle, and characteristics. It explains the different modes of operation, input and output characteristics, important equations, and applications of BJTs. The CE configuration is noted for its high voltage and current gain, making it a popular choice in analog circuits.

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jmhonishkumar
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10 views3 pages

BJT CE Mode Explanation

The document discusses the operation of a Bipolar Junction Transistor (BJT) in Common Emitter (CE) mode, highlighting its configuration, working principle, and characteristics. It explains the different modes of operation, input and output characteristics, important equations, and applications of BJTs. The CE configuration is noted for its high voltage and current gain, making it a popular choice in analog circuits.

Uploaded by

jmhonishkumar
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Operation of BJT in Common Emitter Mode with Characteristics

1. Introduction

A Bipolar Junction Transistor (BJT) is a three-layer, two-junction semiconductor device used for

amplification and switching.

The Common Emitter (CE) configuration is the most widely used because it provides high voltage

and current gain.

In CE mode:

- Input is given between base and emitter.

- Output is taken between collector and emitter.

- Emitter terminal is common to both input and output.

2. Circuit Diagram of BJT in Common Emitter Configuration

(Schematic representation included separately)

3. Working Principle of CE Mode

- Base-emitter junction is forward biased.

- Collector-base junction is reverse biased.

- A small base current (Ib) controls a large collector current (Ic).

- Ic = beta × Ib

4. Modes of Operation

- Active Region: BE forward biased, CB reverse biased. Used for amplification.

- Saturation Region: Both junctions forward biased. Acts as closed switch.

- Cut-off Region: Both junctions reverse biased. Acts as open switch.


5. Input Characteristics (Ib vs Vbe)

- Similar to a diode curve.

- As Vbe increases, Ib increases non-linearly.

- Shows low input resistance (a few hundred ohms).

6. Output Characteristics (Ic vs Vce)

- Shows how Ic varies with Vce for different Ib values.

- Active region: Ic remains nearly constant as Vce increases.

7. Important Equations

- Ic = beta × Ib

- Ie = Ib + Ic

- Voltage gain = DeltaVout / DeltaVin

- Power gain = Voltage gain × Current gain

8. Applications

- Audio and RF Amplifiers

- Signal Processing

- Switching Circuits

- Oscillators

9. Advantages

- High voltage and power gain

- Phase inversion (180° out of phase)

- Versatile and commonly used


10. Conclusion

The Common Emitter configuration of BJT allows efficient amplification with high gain. It is widely

used in analog circuits for its reliability and performance.

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