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Base emitter voltage and collector current

by ranju
Tags: base, collector, current, emitter, voltage
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ranju
#1
Aug2-14, 07:32 AM
P: 91
Does decrease in value of base-emitter voltage decreases collector current..??
As I studied that decrease in base-emitter voltage of some part of signal to lesser ammplification of that part due to smaller current..but how base emitter voltage is leading to less collector current..
because if base-emitter voltage decrease , base current increase which further increase collector current..
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NascentOxygen
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Aug2-14, 07:39 AM
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Quote Quote by ranju View Post
Does decrease in value of base-emitter voltage decreases collector current..??
Yes.

As I studied that decrease in base-emitter voltage of some part of signal to lesser ammplification of that part due to smaller current..but how base emitter voltage is leading to less collector current..
because if base-emitter voltage decrease , base current increase which further increase collector current..
If VBE decreases, base current decreases. It's a p-n junction, so the characteristic is that of a p-n junction diode. If the forward voltage increases, the forward current increases.
ranju
#3
Aug2-14, 08:54 AM
P: 91
But base-emitter voltage is a barrier voltage.. so if it decreases , base current should increase..!!!

dlgoff
#4
Aug2-14, 11:47 AM
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Base emitter voltage and collector current

Quote Quote by ranju View Post
But base-emitter voltage is a barrier voltage.. so if it decreases , base current should increase..!!!
No. NascentOxygen has given you the correct answer. Consider the Base-Emitter Voltage curves:



Check out these Base-Emitter Junction Details.
ranju
#5
Aug2-14, 12:13 PM
P: 91
But is'nt there any logic behind it...??
because if we see this equ.
Ib=Vb/Rb - Vbe/Rb
so from this equ. it can be seen that if Vbe increase base current decrease..!!!
jim hardy
#6
Aug2-14, 03:53 PM
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have you ever run across the formula for current through a junction,
I=eqv/kt
where v would be your Vbe ?
That's what dlgoff's graph is showing you.


because if we see this equ.
Ib=Vb/Rb - Vbe/Rb
so from this equ. it can be seen that if Vbe increase base current decrease..!!!
that involves not only Vbe but an external Vb and an external Rb.

Your original question
Does decrease in value of base-emitter voltage decreases collector current..??
did not involve either.

It is important to be rigorous in your thinking. Focus on the junction, after you've figured it out then add the external components.

Base current and collector current are related by the transistor's Beta,
which itself is a function of collector current.........


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