Re: transistor question...


"Frank Turner-Smith G3VKI" <g3vki@xxxxxxxxxxxxxxxxxx> wrote in message
news:g9jwj.4671$Ef1.1464@xxxxxxxxxxxxxxxxxxxxxxx
on 24/02/2008 17:51 Graham 2E0YSU said the following:
Hello. I have another of those question thingies I would like to ask on
here
about transistors... if you would be so kind...

If the base voltage is increased on an NPN transistor in class B
configuration, the collector current will...

A/ Remain constant?
B/ Decrease a little?
C/ Increase noticeably?
D/ Decrease noticeably?

I would have thought the collector current would remain constant making
the
answer A. I would suppose the emitter current may alter if the base is
increased. Would this make a difference using NPN or PNP or class B or
are
those to make the question look a little more involved?

TIA

--
73
Graham
...--- . ----- -.-- ... ..-


A transistor in Class B mode is biased to its cut-off point so,
(theoretically at least), no collector current should flow.
By 'the base voltage is increased', I assume the examiner means 'the
base-emitter voltage is increased in a positive direction', so the answer
is C, the collector current will increase noticeably. For a PNP device a
negative supply rail is required, and the increase in base-emitter voltage
would have to be in a negative direction. After the increase, either
transistor would no longer be in class B configuration.
--
;-)
73 de Frank Turner-Smith G3VKI - mine's a pint.
http://turner-smith.co.uk


I think its a moot question - without knowing the voltage...


.

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