transistors

It depends on the circuit it's operated in. If you're referring to the device itself alone, those parameters will vary with collector current.

By measurement !

Now, maybe you can us about the reason behind your question.

Graham

my professor measured it using the ratio between Rin and Rs (internal resistance)....i kinda dint understand that...can u xplain me this method??

Why can't you go to the prof., and say, "I still don't get this - can you explain it to me again, in a form I can understand?"

Good Luck! Rich

Frankly, if you want my precise opinion, most 'professors' haven't the tiniest clue about real world electronics and would be better employed cleaning the lavatories than teaching kids who actually want to learn something of value.

I have experienced the same frustration myself (at UCL London would you believe ?) but it was solved by a supposedly 'inferior' teacher at a mere polytechnic who wrote an excellent series of articles on precisely this subject in the reknowned UK magazine "Wireless World". He swept away the usual professor's stuffy nonsense and voodoo and replaced it with simple to understand practical science.

Now, I don't have a reference for those articles I'm afraid but it seems to me that maybe it's time to find out which issues they were in. The approximate time frame for this is the mid 1970s.

Graham

I went to the Prof (age 18) and said (something along the lines of to the best of my memory) why are you using Y parameters when no damn * (OK I didn't say "damn") semiconductor manufacturer publishes any such damn * thing and I think he was mostly embarassed that a student was probably better informed about current practice than he was.

His answer when I suggested that H parameters might be more useful was IIRC "that's another way you can do it". DUH !

What a useless piece of trash ! I had 2 very good friends on the course who both admitted at the end of the first year "I still don't understand what a transistor does". I did and I hadn't learnt it at UCL and that's why I left.

Graham

Connect a battery and a resistor in series with a base emitter junction. Measure the voltage across the resistor and the voltage across the BE junction. From ohms law you can figure out the current flowing into the junction and the resistance of the junction. The BE junction normally operates somewhere between .6 to .7 volts, so keep the BE voltage within that range for realistic values. Over that range of BE voltages , you should see that the resistance of the junction changes. If it didn't change, it would be a simple matter of measuring it with an ohmeter. This is something that you should have done and understood using dry cells and light bulbs long before getting into transistors.

You just measured a DIODE not a transistor.

Please don't flaunt your ignorance in this way.

Graham

Ok so we measured h and not Bh, but the flaunting is not negotiable. thanks

Now you're starting to sound like one of the brothers, here in the states!. Keep it up, you'll be wearing an American patch very soon!

Pay no mind to Mr Ham.. He can be as rude as he can be ignorant.

Frankly, I don't understand the instructor placing a question in suck an awkward manner? In any case. Your idea of applying current in the base, assuming the emitter is at common, is just one step less than that of the final process of measuring the current from source to C.(collector).

This would then give you the current gain ratio. found in reference of Hfe, also found in text as Beta. Now most of us know, that figure is not absolute due to the nature of bipolar transistors.

The above assumes bipolar, since, that is most likely what they teach first in school.

Whereas you can be relied upon to be ignorant and WRONG about everything.

Graham

"Brothers" ? I thought that was a reference to 'black' people.

Not everything American is a bad thing !

Graham

The book, "The Art of Electronics" does an excellent job of explaining how transistors work AND I might add, how to use them in practical applications.

Graham is right. I gave a wrong answere.Unlike some people, I don't have a problem with that. bg

I apologise for my bluntness.

Graham

Well, you may think so how ever, over here black people call white people brothers. That does stir up the pot a bit!

You change your mind like most people change their underwear.

Like I said, most people. That may exclude you.!

I understand that how ever, the procedure you describe even though wasn't correct, was just incomplete of what should have been done in my opinion.

Many people make mistakes how ever, I find that many of them are not due to some one not knowing. They are due to oversight of an error made while thinking ahead to fast.

It's like taking a test.

A person sets up a pool of questions. This person may just be taking references out of a book and only expecting 1 answer..

In many cases, the person preparing the test is not really savvy (hands on) in the field. So in his mind, it's straight forward.

Along comes the victim taking the test.

Now, if this victim studied the same reference materials, that of the question pool. He's going to know only 1 answer how ever, some one that has already been around the barn a few times is going to look at that question and come up with multiple scenarios. which in that case, starts a flame war here.

Nothing directed to you, just an observation i've made here lately.

There are a couple here that change their minds like the wind in New England to suite their daily needs.

Oh well.

Have a great day,.

That's today.

No problem Graham. Thanks for the eye opener. bg