THS4524: unity gain differential amplifier offset?

Hi Mani, 

Are you able to share your circuit schematic? What power supplies are you using and what is the common mode of your input signal? 

Regards, 

Yea Mani, that question is way to open ended to close up. 

1. Full schematic would be required. 

2. DSO? be careful about adding any measurement C to the I/O pins - oscillation hazard. 

3. The layers of output differential DC offset are a little deeper than basic op amps, this attached article tried to step through that - actually found a term I was mistreating in earlier FDA datasheets like the THS4551. 

This was originally a Planet Analog article, but they broke the figure expand links in an Aug. 2019 platform migration - 

https://www.planetanalog.com/dc-precision-considerations-for-high-speed-current-feedback-and-fully-differential-amplifiers-insight-4/

Here is the pdf original, 

DC error considerations for High Speed CFA and FDA's article Dec25 update.pdf

snip of the schematics 

Power supply for the THS4524 here is from an 12V buck to 5V using TPS54521.

Reference is 2.5V from ADS1278(VCOM)

thank you,

Thanks Mani, 

Without running any sims, that 10nF feedback is hazardous from a stability standpoint - if you removed those temporarily, and probed differentially at C467 does the gain look right? 

Also, does the sensor have a DC output impedance we need to include in the analysis?

removed both feedback caps ,seeing offset again-also high frequency noise (3.8 MHz)

For Dc output impedance : its a pressure sensor and it does not have an specs on datasheet.

thanks

Hello Mani,

   Sorry for the delay in response, would you be able to send us scope shots for two circuit setups: without the feedback caps and with feedback caps lowered to 1.5n?

Thank you!

Sima

found this issue in particular to one board only.

same design is working in other boards.

not sure if this is an component malfunction.

thanks

Mani

Hello Mani,

   Thank you for the quick reply! Would you be able to test the device on the boards that work? Or have you already done that and it seems to be the device itself rather than the board?

Thank you,

Sima

Hello Mani,

   Were you able to determine the root of the problem?

Thank you,

Sima 

Its particular to that part.

I had replaced with new one and found to work satisfactory.

Thanks