Hi Dana-san, "Konnitiwa"
Interesting report. I'm trying to do actually.
Result of CMRR
That was measured at output pin.
Calculated CMRR on input pin.
-42.0 - 24 = -66dB (x16)
Anyway, INS-Amp made by PSoC PGA is functionally working.
All depend on user's requirement.
That approach suffers from same issues, accuracy of PGA to PGA
gain tolerances within a single chip. So yes, you can measure
reasonable CMR in a specific device, but based on datasheet specs,
since there is no spec PGAx/PGAy worst case G error, one is stuck
with datasheet for guarenteed performance, and as shown is poor.
And this discussion so far excludes AC CMR.
I will model the 2 OpAmp case to see what it looks like.
Of course the other issue you have is the direct injection of
Vdd/2 noise into first PGA, not a preferred topology. If G needed
<= 8 using A/D differential front end as IA replacement would be a
Three OP Amp case! I am lookin forward.
The first issue with PGA being used in 2 OpAmp IA implementation -
Here is the Matlab analysis, PGA G = 2, 2% error used (even though datasheet
only has a value for G = 1 ), again only PGA G = 2 will work for IA solution :