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shrtrnd

Jan 15, 2010
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Trick question.
Curve tracer will show the operating curve (which is not linear)
Transistors or designed to be used IN THE LINEAR OPERATIONAL CURVE of the transistor output curve.
There will be a portion of the curve where the transistor output is linear.
Hard to answer that question, without knowing what the transistor is doing (as described above).
 

ans

Nov 25, 2010
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If transistor is under active region then it is called a linear device.
 

lexroxas

Apr 15, 2011
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It is generally a linear device. Depending on how you bias the transistor and the temperature of the transistor, it sometimes become a non-linear device.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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It's never really linear. It's just sometimes more linear than other times. And we can take steps to cancel out most of that non-linearity anyway.
 

lexroxas

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At the active region the response curve of a transistor will show linearity and if you can stabilize the temperature and provide proper biasing, you can have a stable value of beta. Beta is the amplification factor and its greatly affected by temperature. A small signal-analysis of a transistor will show linearity in the active region and large-signal analysis will show non-linearity.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Take a look at a circle. The line is obviously curved. Get closer and closer and eventually the line will appear straight.

Whilst at some scale it may appear straight, and for local calculation the tangent is indistinguishable from the secant, the line is still a curve.

lexroxas tells us the line is straight, I tell you the line is curved, but we may be able to assume linearity.

EDIT: Lexroxas and I are now arguing about how many angels can dance on the head of a pin. This is the point where theory and practical models differ, but so little that you can ignore the difference. Curiously, in another thread we are taking exactly opposite sides of a very similar argument :D
 
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lexroxas

Apr 15, 2011
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For heaven's sake. Talking about the good old semiconductor transistors, Does this mean that transistor books never mention about a transistor being linear at all? Of course it does! If you will take into account the dark saturation current and all its external parasitic capacitance, inductance, internal parasisitc shunt and series resistance, temperature, minority carriers due to imperfections on manufacturing .... then you will indeed have a non-linear curve at a very close investigation of the curve. If you look into any semiconductor device at a atomic level then it will be indeed non-linear. But these very very small non-linear response can be ignored in most cases and that's what most electronics book authors agree. If a very simple question is raised by an inquirer and answered by all of these factors that affect linearity then the inquirer will have to understand the very mathematical physics of semiconductors. You said it yourself that "It's just sometimes more linear than other times", and that is at the ACTIVE region and most transistors are operated at this region. It's a simple question that only requires a simple answer.
 

lexroxas

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For the readers, discussions like these are actually very helpful and enlightening and will give you insights from different members. It takes into consideration when to consider a transistor a linear device and when it is being called a non-linear device. If one is going to use a transistor, then one is most likely use it under it's active region. But as I have said before, operations at active region doesn't mean its always linear. One has to consider small-signal and large signal analysis of the subject transistor.
 
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