Electronics > Projects, Designs, and Technical Stuff

New favourite opamp for measuring equipment - AD8605ARTZ

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magic:

--- Quote from: ddavidebor on September 05, 2019, 01:20:38 am ---Curiously, the TP2311 chinese opamp claims much better CMRR than both https://datasheet.lcsc.com/szlcsc/1907250931_3PEAK-TP2311-TR_C116439.pdf
To be trusted? mmh...
--- End quote ---
It's weird. On one hand, they say 106dB typical at 2.5V. On the other, their CMMR vs input voltage plot shows 150dB at 2.5V and CMRR vs frequency says 160dB at DC :-//
And they are very careful not to say anything about CMRR at the input stage crossover point.


--- Quote from: Kleinstein on September 05, 2019, 06:32:05 am ---For the CMRR data it is a little had to tell if this is to trust. It is not impossible to get very good values if something like a bootstrapped cascode is used. The very low THD value also suggest good CMRR. So it is not only that one number.

--- End quote ---
THD+N is only specified at 1Vpp at unity gain, though.


--- Quote from: Kleinstein on September 05, 2019, 06:32:05 am ---By the way: the CMRR value for the AD8605 also look a little odd - it looks better than graph for offset via common mode voltage.

--- End quote ---
Well, the difference between offset at 0V and at 5V is about 50µV. Dividing it by 5V we get box method CMRR of 100dB typical |O :-DD

ddavidebor:

--- Quote from: magic on September 05, 2019, 09:05:22 am ---
--- Quote from: ddavidebor on September 05, 2019, 01:20:38 am ---Curiously, the TP2311 chinese opamp claims much better CMRR than both https://datasheet.lcsc.com/szlcsc/1907250931_3PEAK-TP2311-TR_C116439.pdf
To be trusted? mmh...
--- End quote ---
It's weird. On one hand, they say 106dB typical at 2.5V. On the other, their CMMR vs input voltage plot shows 150dB at 2.5V and CMRR vs frequency says 160dB at DC :-//
And they are very careful not to say anything about CMRR at the input stage crossover point.



--- End quote ---

I've written 3PEAK out of curiosity... let's wait and see...

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