real working of transisitors

[sanjoealex]

Usually we say atransistor is in saturation when its collector-base jn
and emitter basejunction are forward biased.But if CB jn is forward
biased,the current should flow as in a diode but it doesn't. The
transistor should behave as if two diodes are kept in opposite
direction.But it doesn't.Why???? Can somebody help me with this?

 

[Ben Moss]

These links may answer your questions (they certainly explain it
better than I would be able to):

http://electronics.howstuffworks.com/diode4.htm

http://en.wikipedia.org/wiki/Transistor

HTH,
-Ben

 

[sanjoealex]

But still i can't get an answer to my question. I have searched many
textbooks and sites and still i couldn't find an answer. My doubt is
that the current in CB junction of a transisitor doesn't flow as in a
diode even though the collector base junction is forward biased. Why
is this so......???? The sites which were listed here didn't provide
me with the required information.

 

[Rich Grise]

But still i can't get an answer to my question. I have searched many
textbooks and sites and still i couldn't find an answer. My doubt is
that the current in CB junction of a transisitor doesn't flow as in a
diode even though the collector base junction is forward biased. Why
is this so......???? The sites which were listed here didn't provide
me with the required information.

That's because nobody does what you're asking about. The thing you're
looking for is meaningless, unless you're using the transistor in
upside-down mode, and there has been no indication that you even have
a clue what that is.

In normal operation, the collector-base junction is reverse
biased. Current through the base-emitter junction influences
the flow of current from emitter to collector (or from collector
to emitter, depending on your POV), such that it amplifies. So
the collector-base junction isn't even _supposed_ to act like
a diode.

If you hook the transistor in upside-down mode, swapping the
collector and emitter, then the base-collector junction will
be forward-biased, and will act very much like an ordinary
diode, and in many cases, the transistor will even transist,
but it's generally not recommended to try to use them that
way unless the transistor was designed for it.

 

[sanjoealex]

That's because nobody does what you're asking about. The thing you're
looking for is meaningless, unless you're using the transistor in
upside-down mode, and there has been no indication that you even have
a clue what that is.

In normal operation, the collector-base junction is reverse
biased. Current through the base-emitter junction influences
the flow of current from emitter to collector (or from collector
to emitter, depending on your POV), such that it amplifies. So
the collector-base junction isn't even _supposed_ to act like
a diode.

If you hook the transistor in upside-down mode, swapping the
collector and emitter, then the base-collector junction will
be forward-biased, and will act very much like an ordinary
diode, and in many cases, the transistor will even transist,
but it's generally not recommended to try to use them that
way unless the transistor was designed for it.

But even then the transistors used in switching purposes(in the
manufacture of gates for eg do enter into the saturation mode where
both the CB and BE junctions are forward biased. What will happen
there??? Will the CB junction conduct the way a forward biased diode
conducts????????