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Please help! - In the given figure, given that VBBsupply can vary from 0 to 5.0 V,, The minimum base current an - Electronic devices - JEE Main

 In the given figure, given that VBB supply can vary from 0 to 5.0 V, V_{CC} = 5 V ,\beta _{dc} = 200, R_{B}= 100 k\Omega , R_{C} = 1 k\Omega \ and \ V_{BE} = 1.0 V , The minimum base current and the input voltage at which the transistor will go to saturation, will be, respectively : 

  • Option 1)

    25 \mu A and 3.5 V

  • Option 2)

     25 \mu A and 2.8 V

  • Option 3)

    20 \mu A and 2.8 V

  • Option 4)

    20 \mu A and 3.5 V

Answers (1)
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Relation between emitter current ,Base current,collector current -

I_{E}= I_{B}+I_{C}
 

- wherein

I_{E}=Emitter\: Current

I_{B}= Base \: Current

I_{C}= Collector \: Current

At saturation V_{CE} = 0

V_{CE} = V_{CC}-I_{C}R_{C}

\Rightarrow V_{CC}=I_{C}R_{C}

I_{C} = \frac{5V}{1\times 10^{3}} = 5\times 10^{-3}A

I_{B} = \frac{5\times 10^{-3}}{200} = 25\mu A

We known that

V_{BB} = I_{B}R_{B} + V_{BE}

R_{B} = 100K\Omega

V_{BE} = 1V

So V_{BB} = 25\times 10^{-6}\times 100\times 10^{3}+1 = 2.5+1 =3.5V

So  V_{BB} =3.5V and I_{B} = 25\mu A

 

 


Option 1)

25 \mu A and 3.5 V

Option 2)

 25 \mu A and 2.8 V

Option 3)

20 \mu A and 2.8 V

Option 4)

20 \mu A and 3.5 V

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