Homework help.. Electrical Engineers

[jasonRose 0]

If any one is good at solving Opamp problems I need some help. I have an exam monday and I am stuck on a sample problem.

Please Help

Some day I will have the best staff in the world!!!

[SarahC07 0]

12

[jasonRose 0]

When I get stuck on the exam I will default to your answer..

Some day I will have the best staff in the world!!!

[SarahC07 0]

Glad I could help!

[popsjumper 2]

Damn...you're asking me to go back 30+ years?
My EE data banks were overwritten years ago.

I'm down to about 2K of memory now...just enough to remember pull time.

My reality and yours are quite different.
I think we're all Bozos on this bus.
Falcon5232, SCS8170, SCSA353, POPS9398, DS239

[Tokter 0]

I'm rusty too, but that's my guess:

Vo = (Vos+Vp * sin(omega t)) * (R2/R1+1)

[billvon 2,407]

The basics:

Set the + input equal to the - input
Assume zero current flow at both pins
That gives you the voltage at the - pin. Solve for the output voltage by using the voltage divider relationship: Vout = Vin (R2/(R1+R2))) (although in this case R1 and R2 are reversed!)

[ladydyver 0]

geez rosie...you really are desperate aren't you

DPH # 2
"I am not sure what you are suppose to do with that, but I don't think it is suppose to flop around like that." ~Skootz~
I have a strong regard for the rules.......doc!

[vskydiver 0]

Dang Rosie! I just now saw this. I wish you would have just PMed me with your question yesterday. I could have gotten you a more timely answer. Hope it's not too late.

So, what this is is an op-amp based voltage amplifier. An op-amp (drawn as a triangle with a + and - sign on one side) connected in negative feedback (with its output connected back around to its negative input) will tend to equalize the two inputs. Meaning that we can consider the two input values (i.e. the voltage nodes connected to the + and - terminals of the op-amp) to be equal.

From there, the problem gets more straightforward, since it is generally just solving the voltage divider equation. From the voltage divider equation, we know that V- = Vo * R1/(R2+R1), or that Vo = V- * (R2+R1)/R1. (I can go into more detail on that point if it's needed.)

The input voltage is going to be Vos+Vp*sin(omega t), if I'm reading the schematic correctly. The amplifier will then amplify that by a factor of (R2+R1)/R1. This will give you the output voltage. The maximum output voltage will therefore be ((R2+R1)/R1)*(Vos+Vp), and the minimum will be ((R2+R1)/R1)*(Vos-Vp). Note that, because the supply voltage on the op-amp is +/- 10V, that will limit the output, so if either of the voltages is outside of that range, they'll be clipped.

I think that's all that the question is asking. I'm not sure why the Slew rate is given, if the frequency of the input wave is not. I also think you'll need to know the value of Vp to find the maximum output swing.

Note: I'm an Electrical Engineer, and and one whose been spending too much time around other EEs as of late. All the words above make sense to me. They may not make sense to everybody.


**OK, just so you know, I'm not the whiz who solved your problem. However I do surround myself with extremely knowledgeable people. That one came from a Senior at Olin College of Engineering.

[SuFantasma 0]

Pull requires a single-bit operation, unless you are doing forward-error-correct (FEC) based on cyclic-redundancy-check (CRC) of the output stream.

Thus, the pull bit should transition from TTL 0 to TTL +5 on a single sample, or remain TTL +5 for the duration of the digital DUH ! factor, which in your case could be significant. Well, if the pull bit does trigger the correct action and the resulting deceleration is outside nominal parameters, the trailing CRC should indicate and error condition, for which you will require the remaining (2 * 1024) - 1 bits.

Y yo, pa' vivir con miedo, prefiero morir sonriendo, con el recuerdo vivo".
- Ruben Blades, "Adan Garcia"

[ladydyver 0]

I was just saying to doc....."holy fuck - look at V's response" I knew you were talented but geez....btw will send you those pics in the next day or two.

DPH # 2
"I am not sure what you are suppose to do with that, but I don't think it is suppose to flop around like that." ~Skootz~
I have a strong regard for the rules.......doc!

[vskydiver 0]

Quote

I was just saying to doc....."holy fuck - look at V's response" I knew you were talented but geez....btw will send you those pics in the next day or two.

I know huh!

[drdive 0]

Uh, Jason, that shit is greek to me.
I must say, Valinda impressed the heck out of me.

Ya need some Valium or Hydro's to help while you figger this one out?????

If you go into atrial fibrillation, or somethin, give me a shout and maybe I can act intelligent about something.

Doc

"We saved your gear. Now you can sell it when you get out of the hospital and upsize!!" "K-Dub"

"

[ladydyver 0]

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Quote

I was just saying to doc....."holy fuck - look at V's response" I knew you were talented but geez....btw will send you those pics in the next day or two.

I know huh!

but could you have answered the question if asked at the bonfire the other night?

DPH # 2
"I am not sure what you are suppose to do with that, but I don't think it is suppose to flop around like that." ~Skootz~
I have a strong regard for the rules.......doc!

[drdive 0]

V was slurring her speech at the bonfire.

"We saved your gear. Now you can sell it when you get out of the hospital and upsize!!" "K-Dub"

"

[vskydiver 0]

Quote

but could you have answered the question if asked at the bonfire the other night?

Yes! But I would have still had to use my phone a friend option.

[jasonRose 0]

Thanks V. You win the prize.

It ended up being a easy answer... Your "Phone a friend" nailed it!!

"Note that, because the supply voltage on the op-amp is +/- 10V, that will limit the output, so if either of the voltages is outside of that range, they'll be clipped."

The answer is 10 volts.

The reason the SR and other crap was given is because it was a larger problem and I only posted part of it. I couldn't remember how the heck to figure max swing so I was stuck....


For the record: Valinda your the bomb!!!!



Thanks

Beth, yes I was desperate, I spent about an hour going in the wrong direction.......

Some day I will have the best staff in the world!!!

[ladydyver 0]

Quote

Thanks V. You win the prize.

It ended up being a easy answer... Your "Phone a friend" nailed it!!

"Note that, because the supply voltage on the op-amp is +/- 10V, that will limit the output, so if either of the voltages is outside of that range, they'll be clipped."

The answer is 10 volts.

The reason the SR and other crap was given is because it was a larger problem and I only posted part of it. I couldn't remember how the heck to figure max swing so I was stuck....


For the record: Valinda your the bomb!!!!



Thanks

Beth, yes I was desperate, I spent about an hour going in the wrong direction.......

......you are confusing me with Beth?....must be the boobies believe me if you are going to confuse me with someone that is the best person you can confuse me with rosie

DPH # 2
"I am not sure what you are suppose to do with that, but I don't think it is suppose to flop around like that." ~Skootz~
I have a strong regard for the rules.......doc!

[TheAnvil 0]

Valinda, I read your response with dropped jaw until the last line.

Hope you, John, and the family are well!

Smiles,

Vinny

Vinny the Anvil
Post Traumatic Didn't Make The Lakers Syndrome is REAL
JACKASS POWER!!!!!!

[vskydiver 0]

Well, I hope you were able to use that info. I felt like I was a little late in getting it to you. You have my phone number!

[McBeth 0]

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Quote

Beth, yes I was desperate, I spent about an hour going in the wrong direction.......

......you are confusing me with Beth?....must be the boobies believe me if you are going to confuse me with someone that is the best person you can confuse me with rosie

I was quite confused when I read that and had to go re-read the whole thread!

Sorry I couldn't help ya Rosie... I was a ChE and only took very very very limited EE courses. But if you have more calc problems let me know

[DrewEckhardt 0]

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If any one is good at solving Opamp problems I need some help. I have an exam monday and I am stuck on a sample problem.

Please Help

There's a limit to how close amplifier output can swing to either supply rail and you're starting with a DC offset.

There's a limit to how fast voltage can change. Each cycle is 2 pi radians. Omega is angular velocity in radians per second. The op-amp isn't going to overshoot. You can figure out where the limit is and specify a step function where you get circuit gain at or below some value of omega and something else based on the slew rate and frequency above.

You might read _Op amps for everyone_ by Ron Mancini. It's available on-line and has the back ground on everything you forgot (school as a long time ago) or didn't learn (computer science students weren't trusted with soldering irons and only had a few digital classes in the EE department).