what happens when you conenct an circuit with a independant current source to an op-amp?

[Goosemaster]

I get the whole voltage amplification thing. As far as current goes though, I know that the output current is the negative of the value of the resistor that circumvents the op-amp over the resistor that comes before the parallel circuit consisting of the op-amp and the circumventing resistor....The key is, this is all based on voltage sources, which by ohms law, are a function of current.

My question, once again, is what if you hook up a generator and setup a current source?


*in the middle of learning about this and not sure if he made ANY fing sense*

 

[Goosemaster]

So electrical freaks in here? or are they all studying :roll:


I bet they are

 

[ebaycj]

Originally posted by: Goosemaster
So electrical freaks in here? or are they all studying :roll:


I bet they are

Nope, theyre all watching the Bears get their asses handed to them by a 1-4 team.

EDIT: In 1080i hi-def.

 

[Rubycon]

I had to take one of my x-over boards out today with a noisy TL072ACP. Even Solen caps can get leaky. Must be that ocean air. :laugh:

 

[Special K]

I could help if you drew a labeled schematic or something. Your written explanation is too confusing

 

[Regs]

Would you take advice from the communications operator in "Down Periscope" on the submarine?

Well, I'm your guy!

 

[Goosemaster]

Originally posted by: Special K
I could help if you drew a labeled schematic or something. Your written explanation is too confusing

I agree...let me whip somethign up....

 

[Goosemaster]

Originally posted by: ebaycj

Originally posted by: Goosemaster
So electrical freaks in here? or are they all studying :roll:


I bet they are

Nope, theyre all watching the Bears get their asses handed to them by a 1-4 team.

EDIT: In 1080i hi-def.

I saw that too..wtf.....the redskins REALLY pissed me off though...more than the bears

 

[Special K]

Originally posted by: Goosemaster

Originally posted by: ebaycj

Originally posted by: Goosemaster
So electrical freaks in here? or are they all studying :roll:


I bet they are

Nope, theyre all watching the Bears get their asses handed to them by a 1-4 team.

EDIT: In 1080i hi-def.

I saw that too..wtf.....the redskins REALLY pissed me off though...more than the bears

Is this what you are trying to do:

schematic.JPG

 

[Goosemaster]

Originally posted by: Special K

Originally posted by: Goosemaster

Originally posted by: ebaycj

Originally posted by: Goosemaster
So electrical freaks in here? or are they all studying :roll:


I bet they are

Nope, theyre all watching the Bears get their asses handed to them by a 1-4 team.

EDIT: In 1080i hi-def.

I saw that too..wtf.....the redskins REALLY pissed me off though...more than the bears

Is this what you are trying to do:

schematic.JPG

Yeah...exactly. Would you find the thevenin equivalent of the controlled-source and the first resistor?

 

[Special K]

Originally posted by: Goosemaster

Originally posted by: Special K

Originally posted by: Goosemaster

Originally posted by: ebaycj

Originally posted by: Goosemaster
So electrical freaks in here? or are they all studying :roll:


I bet they are

Nope, theyre all watching the Bears get their asses handed to them by a 1-4 team.

EDIT: In 1080i hi-def.

I saw that too..wtf.....the redskins REALLY pissed me off though...more than the bears

Is this what you are trying to do:

schematic.JPG

Yeah...exactly. Would you find the thevenin equivalent of the controlled-source and the first resistor?

You mean the current source? That is an independent source. If I was going to analyze this circuit, the first thing I would do is use the virtual short and ground assumptions and replace the opamp with its equivalent model:

Slide2.JPG

 

[jmcoreymv]

My guess without actually analyzing it is that depending on the value of the current source (if Rf * I is greater than the max negative rail voltage), it would saturate. Otherwise Vout = -Rf*I

 

[Goosemaster]

Originally posted by: Special K

Originally posted by: Goosemaster

Originally posted by: Special K

Originally posted by: Goosemaster

Originally posted by: ebaycj

Originally posted by: Goosemaster
So electrical freaks in here? or are they all studying :roll:


I bet they are

Nope, theyre all watching the Bears get their asses handed to them by a 1-4 team.

EDIT: In 1080i hi-def.

I saw that too..wtf.....the redskins REALLY pissed me off though...more than the bears

Is this what you are trying to do:

schematic.JPG

Yeah...exactly. Would you find the thevenin equivalent of the controlled-source and the first resistor?

You mean the current source? That is an independent source. If I was going to analyze this circuit, the first thing I would do is use the virtual short and ground assumptions and replace the opamp with its equivalent model:

Slide2.JPG

But we are dealing only i ntheory so we were told that R2 would approach infinite resistance....giving us feedback or whatever, so if anything, we would be FORCNIGN the inclusion the the op-amp calculation

V(output) = -r2/r1 , no? or was that I (output) ?

I forgot what the current was...jsut learned it today so I need to go and study

 

[Goosemaster]

Originally posted by: jmcoreymv
My guess without actually analyzing it is that depending on the value of the current source (if Rf * I is greater than the max negative rail voltage), it would saturate. Otherwise Vout = -Rf*I

Out teach briefly mentioned saturation with some pretty graphs depitcing external voltage and current power sources for the op-amp, which conveniently, wouldn't exist in our theoretical analysis,and I got lost there, not knowing whole-heartedly what saturation meant in this context



<---needs to study

 

[jmcoreymv]

Originally posted by: Goosemaster

Originally posted by: jmcoreymv
My guess without actually analyzing it is that depending on the value of the current source (if Rf * I is greater than the max negative rail voltage), it would saturate. Otherwise Vout = -Rf*I

Out teach briefly mentioned saturation with some pretty graphs depitcing external voltage and current power sources for the op-amp, which conveniently, wouldn't exist in our theoretical analysis,and I got lost there, not knowing whole-heartedly what saturation meant in this context



<---needs to study

In that case, if there's no saturation, my guess is that the output voltage would be -Rf*I, it looks basically like a Transimpedance amplifier (with an extra resistor out front).

 

[Goosemaster]

Originally posted by: jmcoreymv

Originally posted by: Goosemaster

Originally posted by: jmcoreymv
My guess without actually analyzing it is that depending on the value of the current source (if Rf * I is greater than the max negative rail voltage), it would saturate. Otherwise Vout = -Rf*I

Out teach briefly mentioned saturation with some pretty graphs depitcing external voltage and current power sources for the op-amp, which conveniently, wouldn't exist in our theoretical analysis,and I got lost there, not knowing whole-heartedly what saturation meant in this context



<---needs to study

In that case, if there's no saturation, my guess is that the output voltage would be -Rf*I, it looks basically like a Transimpedance amplifier (with an extra resistor out front).

I don't know what the end of that statement means


*runs off to sleep and study his ass off tomorrow since he has a quiz on wednesday*