How to measure current...

Dear VIRAJ PANCHEL,

VIRAJ PANCHAL said:

but I am not able to use this method because if i put the resistor there then my Vbias value also varying so i can't use this method so is there any other method to measure current at output...?

Is there a reason you cannot insert a current probe between your output pin of the symbol "OpAmp" and node bias? Alternately, you may save the output terminal of the symbol "OpAmp" and plot its current.

Perhaps you have a reason that I am not understanding for not choosing either of these two methods to measure the current through the output pin of symbol "OpAmp" connected to node bias. If so, I apologize for my lack of understanding and suggestions.

Shawn

Thank you for response, forget about above text how do you measure current at Vbias...?

Dear VIRAJ PANCHAL,

I am not clear at all what your comment means concerning "forget about above text". 

VIRAJ PANCHAL said:

how do you measure current at Vbias...?

I thought I just outlined two methods to measure the current through the output pin of your symbol "OpAmp". With respect to "measure current at Vbias", one measures the current between two nets not at one net - so I am not sure which current you want to measure. Your node "Vbias" is not connected to any other node than the output pin of your symbol "OpAmp" and your feedback resistor R19. Hence, the current flowing into or out of the output pin of your symbol "OpAmp" is equal, but opposite in sign to the current flowing out or into resistor R19.

Maybe I am still not understanding your question? Perhaps your question is understood by other Forum members.

Shawn

No problem, and thank you for your answer.

Dear VIRAJ PANCHAL,

I just hope it was helpful as I was not sure I was understanding your main question! 

Good luck simulating...

Shawn

Thank you for your affect to understand my question.

I found one image that shown my question..!!

please look it below circuit, in that circuit I want to measure the current on "Z" label. so how can I do this...? you can see the circuit around the "Z" label, so I am looking this for this to my circuit, in my opamp circuit (mention in above conversation), I want to measure current on "Vbias"  label. Now I think you may be more understand my question... 

You can select the current through that pin (it's not a "label") by selecting Outputs->To Be Plotted and clicking on the instance pin at the level above (this will draw a circle around the instance pin which will also show up in the level below when you descend). If this is at the top level, you can't do this - mainly because it would make no sense (as there's nowhere for the current to flow - so you can't measure the current through anything).

It's not clear whether your schematic in the original post is the top level or from a sub-block. If it's a sub-block, then click on the Vbias pin on the instance at the level above.

Andrew

Thank you. It's really helpful.