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19th March 2009, 02:00 #1
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ua741 pspice
hey guys i just wanna ask..i got some questions using pspice to find some practical opamp limitations with opamp uA741..the problem is now..i already construct the circuit as given in my tutor..but i didn't get the simulation of this circuit..can u help me?
is there anything to do with the specifications of the opamp? or maybe i have to change any setting for the opamp??..here i attach my circuit

19th March 2009, 02:00

19th March 2009, 08:19 #2
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pspice ua741
What really is your problem ? What is the question ?

19th March 2009, 13:36 #3
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pspice opamp
my question is actually to study some practical opamp limitations using ua741 in pspice..for this questions we have to find input offset volatge,input bias current and input offset current..but my 1st problem now is that..when i construct the circuit given in pspice..for the simulation part, i only get a straight line..supposely i should get sine wave curve..can you help me??is there any specification of pspice i should change when we use ua741 to get result??

19th March 2009, 14:14 #4
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opamp pspice
Originally Posted by absoluteawesome
You have the task to reveal by simulation which of the real parameters have been implemented in the simulation model for the 741 opamp, right ?
1.) I had a look on your schematic and I see a 5 volts dc source at the input (at R1) of the inverting circuit . Why ?
2.) And why do you expect a sine wave ?
I don´t see any sine wave source !
3.) What is the reason for both resistors of 5 kOhms ? My question is, because I think you are going to simulate the opamp without feedback; am I wrong ?
4.) If you like to get results for offset and bias parameters, it is absolutely important for you to know the exact DEFINITIONS for these parametrs.
Do you know them ?

19th March 2009, 18:30 #5
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ua741 in pspice
You may want to use a VSIN source instead of a VDC source for Vs, assuming you're performing a transient analysis? Also the purpose of the 1 µΩ resistor is dubious. As you see from the node voltages, it's generating a ridicolous voltage drop of 80 fV, but it doesn't hurt, of course.

19th March 2009, 18:30

21st March 2009, 11:21 #6
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pspice and opamps
Here i attach my question for you guys to refer..
really appreciate it, if you guys could help me with this one..hope the questions are more clearer to understand..
I just wanna know is there any setting in pspice i should change? and about the PARAMATER u said before..what is it actually?

21st March 2009, 13:55 #7
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ua741 en spice
Originally Posted by absoluteawesome
However, it is necessary to know the DEFINITIONS !
Therefore my question to you: Do you know, for example, the definition for offset voltage and offset current ? If not, this is the first step you should take.

21st March 2009, 13:58 #8
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opamp ua741
im not too sure about that..can u guide me?? i mean explain it to me..really appreciate it so much!

21st March 2009, 20:40 #9
opamp ua741
wow, dude you gotta do your homework first. spoon feeding is painful.
read this very carefully: when it comes to simulations, you MUST know what to expect before you hit the 'run' button.
if you do not know what to expect then you are a useless engineer. if you are a student, then you are just getting by, get your A, get into the work force and then become a useless engineer.
i am not being harsh (ok, i am a little bit) but please realize i am trying to give you the best advice you need at this point in your long career. do your homework, understand what you are doing. hand calculations to see what values you should get.
then simulate the circuit and confirm your hand calculations.
then if you still have questions post them here.
Mr.Cool

22nd March 2009, 10:41 #10
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ua741
Mr. Cool
I completely agree with you. I believe, this forum should not only give some technical advice; in some cases it makes really sense (or even is necessary) to give some recommendation how to learn and how to gather knowledge.
Thanks.

28th March 2009, 11:03 #11
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calculations on ua741
I'm from the same university as the author.
Referring to the attachment(question) above, how I'm going to calculate the Vio for condition a,b, and c?
For condition b and c, since R1// Rf is implemented, do I still need to consider Vos due to input current offset?
Thanks for reading this, any help would be highly appreciated.

28th March 2009, 11:03

3rd April 2009, 12:41 #12
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simulation of op amp
int the circuit in figure 11..
how actually we derive the equation step by step to get the Vo using kirchoff current law?
is it like VoV/RF=Vo/RL
then VoV/Vo=RF/RL
1 + V/V0=RF/RL
V/Vo=RF/RL1 ??????i think something wrong with the equation..
how guys?
the Vo value is there rite?is it Vo=5V
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