I have found two Fully Differential Amplifiers from Texas Instruments. They have very similar names which are THS4531 and THS4531A respectively. I have checked both datasheets and found nothing different. Could anyone tell me why a capital "A" is added? I am not quite familiar with the naming system of TI.

Datasheet links:

THS4531: http://www.ti.com/lit/ds/symlink/ths4531.pdf

THS4531A: http://www.ti.com/lit/ds/symlink/ths4531a.pdf

Many thanks!

  • \$\begingroup\$ Without looking at any of the details I'd guess that the 'A' version is a newer silicon revision and is probably functionally the same. \$\endgroup\$
    – brhans
    Feb 9, 2016 at 17:22
  • \$\begingroup\$ Letters after a part number like this usually mean newer version, usually with better specs. \$\endgroup\$ Feb 9, 2016 at 17:35
  • \$\begingroup\$ @OlinLathrop Though for the dsPIC30F6011/6011A it means they moved the programming pins PGC/PGD to a less stupid pair... \$\endgroup\$ Feb 9, 2016 at 19:27

1 Answer 1


'I have checked both data sheets and haven't found anything different'

Well you haven't checked very carefully , have you?

They seem to be very similar. There is at least one difference, the bias current of the 'A' version is higher than the plain version.

Given that the plain data sheet is dated 2012, and the A version is 2016, I suspect that what has happened is this. They wanted to discontinue the old process that was used to make the plain version, and move the part to a newer, faster, finer process. They would have needed to change the masks to fit the new process, and either couldn't match the previous bias current, or couldn't be bothered to spend the time to, once they had matched all the more important dynamic, gain, distortion, noise, drive current etc etc specifications.

As the new part could fail in some existing circuits, if the customer had designed it right to the very edge on bias current, they gave it a new part number.

I would be willing to bet that the new part does not match the old part in all the parameters it appears to, but is actually better, probably faster, due to the new finer geometry process. But once the new part does better than the old one, there is no real need to change the data sheet. Only for spec degradations is there a possibility of upsetting existing customers.

There is another possibility. Their old process has 'gone bad', and try as they might, they just can't meet the original specifications. This happened with their low noise OPA656. The original device has been in the field for so long meeting specification that they can't just degrade the spec and hope no-one would notice, so it needs a new part number.

  • \$\begingroup\$ Since both product lines are active, I would actually tend to assume that this is a redundant component made by a company TI acquired, but a silicon rev is possible too, they still support the previous process due to the active production state of both components. TI Acquired National Semi in 2011 (a year before the origin date of the -A datasheet) \$\endgroup\$
    – crasic
    Feb 9, 2016 at 17:35
  • \$\begingroup\$ Maybe. Are you volunteering to ask them? If I were retiring a process, I'd run both in parallel for a while to make sure there weren't any unforeseen unforseens. \$\endgroup\$
    – Neil_UK
    Feb 9, 2016 at 17:39
  • \$\begingroup\$ @Neil_UK Thanks for you help. I might get them both and see the actual difference. \$\endgroup\$
    – ppendless
    Feb 10, 2016 at 11:10

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