0
\$\begingroup\$

I've been playing with voltage swings in a basic emitter-follower circuit. If I swing the input too large in the negative cycle, the base-emitter junction is reverse-biased and the transister goes into cutoff mode. I can see the clipping in the output and this makes sense to me. With the collector, however, I've noticed that I can swing higher and not see symmetrcial clipping. Eventually I do see the clipping.

Is there a rule of thumb, like with the base-emitter junction, for managing base-collector junction? May I use VC-VB=0.6/0.7 V for this relationship too?

\$\endgroup\$
2
  • \$\begingroup\$ Take a look at my emitter-follower answer - it shows the assumptions made for that circuit. electronics.stackexchange.com/questions/8656/… \$\endgroup\$
    – W5VO
    Jan 22, 2011 at 8:41
  • \$\begingroup\$ How poor my memory is! Thanks for pointing that out. \$\endgroup\$
    – Dr. Watson
    Jan 23, 2011 at 3:04

2 Answers 2

Reset to default
1
\$\begingroup\$

If you drive the base positive enough (assuming an NPN) what happens is the transistor 'saturates', and the collector voltage will dip to just a couple tenths above the emitter. In this mode, the base-collector junction is actually forward biased, instead of reverse biased as is usually the case.

\$\endgroup\$
1
\$\begingroup\$

BJT is usually asymmetrical.

There is no rules AFAIK, they all different there - so you need to test each type you need.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.