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Amplifier Equivalent Circuit problems :(

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silverusa

New Member
Hey everyone !

I just transferred to another school and Electronics program in new school is a little different.

If anyone can help me get on the right track it would be great.

I need help with :

- Understanding all the questions.
- Picking right equations.
- Meaning of some shortcuts.

etc.

Teacher gave us notes but he seems like a type of person that expect you to know everything.

Once i get on right track i will do rest of the research myself i just need to get started after looong summer.





Thank you !!!
 
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alphacat

New Member
Hey,

I believe that the following drawing should help you out solving most (if not all) of the listed questions.

What in the red rectangle is the two-port model of the amplifier.

Good luck.

 

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Grossel

Well-Known Member
Well, I beleive an inverting opamp amplifier will match the description of the amplifier. Say amplification -Fu = R2/R1. Then we know that input resistance R1 = 50k.

Turn the formula in respect to R2, we get:
R2 = -Fu * R1 = -(-200) * 50k = 10Mohm.

So the circuit will look like this:

NOw the drawing is finnished. Sorry for the time - but found a little bug in inkscape I got to report :)
 

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silverusa

New Member
You guys are great.

How do you recognize what kind of amp just by looking at values ?

When i get home at 10pm from school today :( i will try to get same answers as the ones on the bottom of that page.

What equations would i use and why ?

Thank you !
 

alphacat

New Member
Have you ever heard about terms like controlled-sources, voltage divider?
Its very simple once you have the two-port model drawn.
 

silverusa

New Member
Voltage divider yes. Controlled source i dont think so.

In my old school electronics 1 didnt cover amps at all. I mean we did just overview by the end of the class.

Once i transferred to new school electronics 2 is all about amps and from what i heard electronics 1 also covered bunch of it.

This is why i am having trouble. If i saw how those problems were done it would help me alot.

Thank you
 

alphacat

New Member
I'm sorry to hear that, that kind of sucks.
Its weird that you werent required by the new school to take electronics 1 again in their school, since the syllabuses of these two versions of that course arent similar, apparently.

a controlled source is a source that is cotrolled by some other parameter.
In our case, the conrolled source is a voltage-controlled voltage source, it produces voltage of (-200)*vin.

Once you understand that, and understand the voltage divider formula, i think you are capable of solving at least some of the questions here.
 
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