Bjt npn base collector junction breakdown

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SUMMARY

The discussion centers on the breakdown of the base-collector junction in NPN bipolar junction transistors (BJTs) during forward active mode. It is established that while the base-emitter junction is forward biased, the base-collector junction is typically reverse biased and can indeed break down if the collector-base voltage (Vcb) exceeds a certain threshold. The breakdown voltage is denoted as Vceo, which includes the breakdown voltage of the base-collector junction plus a diode drop from the base-emitter junction. Additionally, water analogies are discussed as a means to explain BJT operation, with varying effectiveness noted.

PREREQUISITES
  • Understanding of NPN bipolar junction transistor operation
  • Familiarity with forward and reverse biasing concepts
  • Knowledge of breakdown voltage terminology
  • Basic grasp of semiconductor physics
NEXT STEPS
  • Research the breakdown characteristics of BJTs, focusing on Vceo and Vbc
  • Explore advanced water analogies for explaining semiconductor behavior
  • Study the effects of varying collector-base voltage on transistor performance
  • Learn about thermal runaway and its implications in transistor operation
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Electrical engineers, electronics students, and anyone interested in semiconductor device behavior and transistor applications.

SpartanG345
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When the NPN is in the forward active mode

The base emitter junction is forward biased and the base collector junction is reverse biased.
But isn't it possible for the base collector junction to break down? Or do we assume it never breaks down?

Also does anyone know any good water analogies that explain BJT's? I found some using google but they seem complicated.

I found this site http://www.satcure-focus.com/tutor/page4.htm
the 1st analogy doesn't seem to work that well when you think about which junctions are reversed and forward biased, but the second analogy seem ok - the one with the pools of water and the base acting as a catalyst to start the water moving

 
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its possible that CB junction breaks down if u increase CB bias voltage . . .
usually collector base junction ll be biased below breakdown
 
SpartanG345 said:
When the NPN is in the forward active mode

The base emitter junction is forward biased and the base collector junction is reverse biased.
But isn't it possible for the base collector junction to break down? Or do we assume it never breaks down?

Also does anyone know any good water analogies that explain BJT's? I found some using google but they seem complicated.

I found this site http://www.satcure-focus.com/tutor/page4.htm
the 1st analogy doesn't seem to work that well when you think about which junctions are reversed and forward biased, but the second analogy seem ok - the one with the pools of water and the base acting as a catalyst to start the water moving


Yes. Vceo is actually Vbc junction breakdown plus a diode drop with Vbe.
 

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