How is the value of BJT base resistor calculated?

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aryajur

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In many circuits when we place a base resistor for a BJT, I know its there to limit the BJT base current. My question is how exactly is the value for that resistor calculated?
 

Re: BJT Base resistor

In many circuits when we place a base resistor for a BJT, I know its there to limit the BJT base current. My question is how exactly is the value for that resistor calculated?
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For a desired Ic = 10mA, and β = 75, Vbe ≈ 0.6 , and Vi = 5 and No Remiter.

So Ib = Ic/β = 10mA/75 = 0.133mA.


Ib = 0.133mA = (5V-0.6)/Rb

Rb = 4.4/0.133mA = 33KΩ
 

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    aryajur

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Re: BJT Base resistor

Ya, it was a stupid question, I got confused when looking at some bandgap circuits.
 

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