SaM - Fast Recap on BJT • Bipolar Junction Transistor

• Source: Youtube (ElectroBOOM)
• Source: Youtube

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Graph

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Memory Card

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In Real Life Image

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Simple Scheme

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Cross Section

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Different Regions of Operation

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Active Region

• Used for amplificiation

• NPN:
  

  • $V_C>V_B>V_E$

• PNP:
  

  • $V_E>V_B>V_C$

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Saturation Region

• Used as a switch, ON: saturation region, OFF: cut-off region
• $V_B>V_E$ & $V_B>V_C$

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Reverse Active Region

• Emitter is reverse biased.
• The amplification provided by the BjT is much less than in active region.

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Symbol

• The arrow indicates the direction of the current, when in the active region
• NPN:
  
• PNP: