2N3904 experiment

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Plan to do this tonight or this weekend possibly this afternoon if I can.

Btw I don't come up with this on my own all credit 💳 goes to the author of the book I'm working out of. 

It took me a long time to get to this point where I'm looking at a circuit and actually making the circuit that HAS A TRANSISTOR      so I'm stoked to say the least.  This will be my first ever  hopefully one of many.

That said let's get on with it.   

A diagram of the circuit I need to make is shown below

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My instructions are to vary VBB until VCE is 6V
by adjusting a variable resistor 

Then measure and or calculate VB, VRC, VRB, IC, IB, Beta, VCB, and VBE

Then after that I do the same with VCE at different values.  Investigating linear, saturation, cut-off etc 

And a lot different cool stuff.

Here's my victims

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Ok first order of business determine pinout

I wanted to go old skool and pretend it was 1970 and no Internet or peak atlas and no datasheet available 

I know it's NPN from the diagram (never points in)

So I just started poking around looking for a base emitter junction then the collector is gonna be the other one.

It looks to me like flat side facing forward the pinout is EBC
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Ok I think I got lucky and spared a slap upside the head by our esteemed member in Tasmania 

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Alright got it hooked up and adjusted

I couldn't get it to work for a while then I figured out I was missing the ground lead on the third pin of the variable resistor


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So I'm off for some probing and calculating

 

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And that's a wrap (I think until one of our esteemed members finds an error in my calculations  )

I was frustrated I could not calculate VBB and gave up and measured it 

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Btw I will be doing many more of these and will spare you the gory details and pics..unless I find something really cool 😎 to get excited about and run through the streets screaming eureka 

So thinking out 🔊📢 loud I'm wondering about a few things that I'm gonna investigate

Did I just bias a transistor?

Is Hfe the same as Beta ?

Also I get it this is very simplified but seems in the future I will be encountering base voltage in alternating current.

Also in this experiment seems kinda like a waste all that emitter current going to ground but yeah there is a lot to be revealed later on fortunately.

 

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Id like to announce a major discovery 

Turns out that a variable resistor turned all the way to zero is a dead short 


fortunately my power supply kicked to zero 



Anyhow I'm back to it same circuit just changing VCE 

[g1]

Turns out that a variable resistor turned all the way to zero is a dead short 


fortunately my power supply kicked to zero 

Did you connect the supply to something other than the diagram in the picture?

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Turns out that a variable resistor turned all the way to zero is a dead short 


fortunately my power supply kicked to zero 

Did you connect the supply to something other than the diagram in the picture?

We have a winner.  No sir pretty sure I messed up and had a lead from the node connected to the middle terminal (I think)

Instead of terminals one and three (10k at all times)
 

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I'm almost to the part in the lab exercises where I'm supposed to do a lot of the same stuff except with a 2n3053 and 2n3055 to see the results of smaller and larger beta.

I have some TO-39 just not 2n3053 and then heck I could buy some 2n3055s but idk how to connect a TO-3 to a breadboard 

Not that it would be impossible but I think I may start checking stuff that I have lying around and try to find some suitable candidates.

I did look up Hfe vs Beta and saw a reference to common emitter circuit but I'm not there yet.

Maybe I can measure Hfe of 2n3904 then try to get a transistor that has lower and greater (they need to be NPN as well)

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I just took a brief inventory of what's on hand.  I guess I just need to jump in and start testing

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[g1]

As far as hfe vs beta, they are the same thing.
Here's a link to a good article on it, note what they say about hfe of circuit.  Usually for substitutions we need a beta greater than what the circuit requires.  Knowing beta of the transistor does not tell us the circuit gain.
https://www.ovaga.com/blog/transistor/what-is-transistor-hfe

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That is a great article thanks

 

[J M Fahey]

Congratulations on your experiments.
Nothing beats hands-on.
Most books are old school (transistors were a BIG novelty in the 50s and 60s) so examples are "dated" but all of those have modern equivalents.
For 2N3053 you can use any modern mid power transistor, think cheap and plentiful TIP31C or similar.

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Thank you sir you are so right I use to work so many problems crunching numbers applying formulas finding theta and crap and was getting nowhere  then I would dream about being in a time machine and going back to university like in 1973 where they had a rigorous lab class.  Then I found these books by Lorne MacDonald that were like a lab class telling me to do stuff 

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Each chapter has concepts and examples of problems and calculations then at the end of each chapter are lab exercises and more problems.

 

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Anyhow I think I was supposed to draw a conclusion after doing another experiment.

I set up another circuit this time with two variable resistors.  First I adjusted VR2 until Vcc was 12V then I had to adjust VR1 until Vce was 9V.  Then take measurements.  After that adjust VR2 so that Vcc was 9V and leave VR1 alone.  Do it again for Vcc at 6V.
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The results
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So...maybe I need to go back and read the chapter text but what I notice is the base current is not affected by the collector voltage. (ya think  )
Oh wait a minute....neither is collector current huh?  Wondering how that is possible 

Now the significance of this concept escapes me at the moment

I presume this is a big deal so I will ponder it for a while.