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What does determine the linearity of bipolar transistor?

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bouchy

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Hi All,

I have couple of questions:

1- What determine the linearity of bipolar transistor?

2- I read that the use of (i.e, RC) feedback in common-emitter transistor can improve the linearity of my transistor. can someone please explain?

Thanks
 

linearity of a transistor circuits

Download this tutorial on BJTs and treat it as a bible:
**broken link removed**

About linearity and other issues in CE configuration (if you din't want to read all the way through, and I ecourage you to read it ..) go to page 98 where you will find this:
Another important consequence of including the resistance Re in the emitter is that it enables the amplifier to handle larger input signals without incurring nonlinear distortion.
Click to expand...
and more ..

regards ..
 

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    bouchy

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negative feedback nonlinear distortion

hello IanP


asper your say,
emitter resistance are used to increase amt of linearity in transistor.


actually it is used to make negative feedback to achieve stable gain.pls throw light in this regard.
 

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    bouchy

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is of bjt

the BJT input linear range is limited in 4Vt range (about 100mV).

When the CE (common emitter) circuit with degeneration with a resistor, then the input range can be improved by a factor of 1+gm*R.

Yibin.
 

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    bouchy

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bjt transistors bible

Hey

If you draw the small signal diagram of the BJT (T-model), then the emitter resister Re is in series with the small-signal emitter resistor. This means that when an input voltage is applied to the base of the transistor it is divided between the two resistanses. This will of cause lower the signal across the small-signal emitter resistance. It is only the voltage across this that is amplified. In this way you can apply larger signals to the BJT and still consider it linear.
The price is of cause gain.
 

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    bouchy

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degeneration resistor re to a ce bjt amplifier

Hi IanP,

How can we go to page 98 in your link ?
I did not succed further than page 6.
regards
g
 

linear range bjt

tyassin said:
Hey

If you draw the small signal diagram of the BJT (T-model), then the emitter resister Re is in series with the small-signal emitter resistor. This means that when an input voltage is applied to the base of the transistor it is divided between the two resistanses. This will of cause lower the signal across the small-signal emitter resistance. It is only the voltage across this that is amplified. In this way you can apply larger signals to the BJT and still consider it linear.
The price is of cause gain.
Click to expand...

Yeah, tyassin gave a good explanation on what happens at small signals analysis.

At large signals analysis, we can see that gain is nonlinear (its angle is not constant). When negative feedback is used, gain is divided by 1+gm.re, so that all the gain curve becomes something closer to linear.
 

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    bouchy

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