I am using PSOC 5LP Kit and i want to implement instrumentation amplifier having high CMRR and Gain. How i can do this?
Looking forward for your suggestions.
Solved! Go to Solution.
Thank you so much for your reply.
Actually i am new on this forum.
Next time i will keep this thing into account.
I am using cypress kit for the first time and it is very interesting. I am just trying to convert my hardware onto this chip.
Sorry! I dont want to click "answer verified" but did it mistakenly. I just wanted to click reply.
i dont know what happened with this.
Does it make anything negative?
I even do not know what the "Answer verified" click does at all (except inserting that note into the post). So nothing to get upset for.
Do NOT use that ap note that Bob posted.
You cannot because of the G mismatch between PGA (if you tried using those)
or the Aol mismatch one OpAmp to another. Depends in latter case how much
CMRR you are willing to forego. In the former case the CMRR is horrible worst
case becuse of G inaccuracy PGA to PGA.
Here is a analysis - http://www.cypress.com/?app=forum&id=2492&rID=82151
Use an external IA. Or a single stage IA with 1 OpAmp and external precision Rs.
But 2 and 3 OpAmp architectures, only use an external IA.
Well, to explain how your IA behaves would need some description of "how" it behaves.
Additionally I would suggest you to post your complete project, so that we all can have a look at all of your settings? To do so, use
Creator->File->Create Workspace Bundle (minimal)
and attach the resulting file.
Unless you dont need much CMR in the input stage do NOT use that solution.
If you do the analysis on this you will get << 20 db CMR because of PGA gain accuracy
as stipulated in datasheet. See the analysis in the earlier post.
Actually i need very high CMRR (More or less 80 to 90 DB).
If This will not work then, is there any other possiblity to get the result near to my desired value?.
I also tried to implement instrumentation amplifier with three op amps but that was was also giving me strange results.
If you use 3 OpAmps and a precision thin film R network for the
Rs you can get approach that level of CMR, but OpAmp AOL
differences and mismatch thermals, offsets, will limit you.
External precision IA is the way to go if you need lots of G and CMR.