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| 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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