So what do you think you have for Vb and Ve? We are not mindreaders, so there's no way we can tell you if you are right or not.PLEASE HELP!
The following circuit is given and I need to solve for VB, VE, and VC. I know it's not a super hard problem but my professor isn't great and I think he confused me more. I think I have VB and VE but verification of these would be nice too.
Thanks!
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I'm not asking you to do my work. I want to know how to do this problem. I have the option to find these values using Multisim, but I am choosing to do the hand calculations instead because I want to know how to do them. My professor just doesn't explain it well. If you'll look at my latest reply to my own thred, you'll see the calculations I've completed thus far.How to start?
First of all produce the formulae for:
IC in relation to IB
Same for IE in relation to IB and IC
Next step is to use Ohms laws to resistors.
Combine the two.
We are not going to do your work!
Yes, we like to help you but it should roll, at the end, out off your brains.
Show us what you have don so far.
Picbuster
Let's set aside the question of whether Vb and Ve are correct or not for just a bit and focus on what you know about Ic.The following equations are what I have done to attempt to solve. The values obtained for Vb and Ve are of very minimal error when compared to my experimental values. (This problem is part of a lab report). I can't wrap my head around any way to find Vc. Even Vcc-VR3 doesn't work because I don't know VR3, nor do I know how to get Ic with the multiple power sources the way they are.
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I tried this:Let's set aside the question of whether Vb and Ve are correct or not for just a bit and focus on what you know about Ic.
If you know Ve, can you find Ie?
What do you know about the relationship between Ic, Ie, and Ib for the transistor (regardless of which operating mode it is in)?
If the transistor is acting in the active region, what do you know about the relationship between Ic and Ib?
Okay, now let's look at your calculations for Ve and Vb.The following equations are what I have done to attempt to solve. The values obtained for Vb and Ve are of very minimal error when compared to my experimental values. (This problem is part of a lab report). I can't wrap my head around any way to find Vc. Even Vcc-VR3 doesn't work because I don't know VR3, nor do I know how to get Ic with the multiple power sources the way they are.
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You have worse problems then that. Last I checked 20 - (-0.00139)(10000) was 33.9.I tried this:
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But this yields a value that is way off from my experimental value which was +4.34 V
It was simply a typo. I entered the result of the multiplication without subtracting it from 20. Thank you for catching that. I understand to check my answers. I also understand that the negative collector current is a red flag, but nevertheless, 33.9 is still far off from my experimental value. It seems you're using this site to condescend rather than help, so I would appreciate a bit more understanding.You have worse problems then that. Last I checked 20 - (-0.00139)(10000) was 33.9.
You need to ask yourself, always, whether your answers make sense?
Does it make sense that you have a negative collector current?
If not, go back and look at why you are using a negative voltage for the voltage ACROSS the emitter resistor. Remember, Ohm's Law deals with voltages ACROSS resistors and currents THROUGH resistors. You can't just throw the nearest voltage value at the equation and expect meaningful results.
I'm trying to help you see how to (1) do you work in a way that minimizes making mistakes in the first place, and (2) review your work so that you have a better chance of catching the mistakes you will still inevitably make (since you, like the rest of us, are only human).It was simply a typo. I entered the result of the multiplication without subtracting it from 20. Thank you for catching that. I understand to check my answers. I also understand that the negative collector current is a red flag, but nevertheless, 33.9 is still far off from my experimental value. It seems you're using this site to condescend rather than help, so I would appreciate a bit more understanding.
A good place to always start is to annotate your diagram so that you have a clear picture of what you are doing (and so that others are working from that same picture so that you can communicate clearly with them).
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Then you need to use these definitions in your work so that you can document and communicate exactly what you are doing.
For instance, if you want the emitter current, then you apply Ohm's Law to the emitter resistor.
\(I_E \; = \; \frac{(V_E \; - \; V_{EE}\)}{R_E}\)
Do you see the mistake you made and how taking the time to clearly define what you are doing can help avoid it?
I apologize for reading your messages as condescension. I understand that you are trying to help. Please help me finish this problem.I'm trying to help you see how to (1) do you work in a way that minimizes making mistakes in the first place, and (2) review your work so that you have a better chance of catching the mistakes you will still inevitably make (since you, like the rest of us, are only human).
If you understand that the negative collector current is a red flag, then you have a red flag telling you that something is WRONG at a step BEFORE you get either -13.91 V or 33.9 V, so it shouldn't be surprising that either of those results is meaningless. You need to focus on getting rid of the red flag before proceeding.
But, since you feel that trying to help you do your work in a clear and organized way that allows you to communicate that work accurately and effectively, or that trying to help you set up your work in a way that reduces the likelihood of making mistakes, or that trying to help you learn how to evaluate your work so as to find and fix the errors that you make constitutes condescension, I won't condescend your work any further. Good luck and goodbye.
by Jake Hertz
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by Jake Hertz