LMC6041: PCN#20250327000.1 clarification

Hi Raymond, 

Many thanks for your reply.

• For the THD the paramter is worth than the previous part but is seems that the test conditions are different if we compare the old part and the new part.

Old part : 

New part : 

Is it possible that the difference is coming from the test conditions ?

• For the input current noise, I'm not very familiar with Amplifiers but we agree that if the value is higher it is worth ?

"from 0.2fA/√Hz to 12.5fA/√Hz" => The new part is worth right ?

BR

Hi Nicolas,

I am unable to say because the old one is specified the minimum THD, the new THD figure is specified as typical. My guess is that the asymmetrical supply rail may have to do with the input Vcm range in the part. It should not be affected by the power rail. THD performance depends on how well the input and output signal ranges stays in a linear region (without signal distortion). 

Nicolas Chevalier said:

For the input current noise, I'm not very familiar with Amplifiers but we agree that if the value is higher it is worth ?

I agree that the input current spectral noise density figures have changes.  LMC6041 is a general purpose op amp and I do not believe that this changes are significant for the op amp and low op amp bandwidth. There are other dominated errors in this part vs. the figure. 

What is your application? If you have a specific design requirement, I can recommend something if you provide the application type and the component cost consideration. 

Best,

Raymond

Hi Raymond,

Sorry my screenshot was not good for the old datasheet 

It is also the typical value for the THD.

In fact i work in the serial life team.

The goal for me is to understand the differences with the new chip, and evaluat if they are minor or not.

The boards are already in production the goal is not to change the part because it will take some times for validations...

Do you have example to evaluate the differents errors of the op amp ?

BR

Hi Nicolas, 

Let me confirm the new 1% THD figure (new FAB) with our formal GPRAMPS team. Now I am a bit skeptical about the THD change, which is 100X in differences between old and new FAB and it is operating in very light load condition at 100kΩ. 

Please give me a few days and I will find out why the new FAB is changed so significantly. 

Nicolas Chevalier said:

The goal for me is to understand the differences with the new chip, and evaluat if they are minor or not.

Please see our Precision Labs op amp video series in Input offset, input bias current and Noise topics. 

https://www.ti.com/video/series/precision-labs/ti-precision-labs-op-amps.html

If you have other questions, please let me know. 

Best,

Raymond

Hi Nicolas, 

I requested the THD information from our validation team - there is a typo in the Vout voltage swing, see the image below. 

The THD figure is worse than the previous part, but 1%THD typical figure is specified very conservatively.

The best way for you is to compare the old vs. new LMC6041's output and check the FFT waveform components. The bandwidth of the part is very low (<75kHz) and it may or may not have much effect in your application. If the THD distortion is outside of your acceptable range, you may have to consider to replace the part. 

If the op amp is used for DC reference application or similar, then %THD differences may not make significant difference. 

If you are able to post the schematic, I will be happy to review it and make any suggestions. 

If you want to keep the discussion in private, please post a "friendship" request via E2E and we can communicate via a secured flatform. 

Best,

Raymond

Hi Raymond, i send you a connexion request to have a private communication it will be better