• State
  • Locked Locked
  • Replies 0 replies
  • Subscribers 48 subscribers
  • Views 312 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Vocm effect on inputs of OPA1632

Azad Chacko
Prodigy 70 points
Other Parts Discussed in Thread: OPA1632

Hi,

I have setup a test circuit based on Fig.11 of the OPA1632 datasheet, It is actually to drive another type of ADC that requires output common mode of 1.65V. So Vocm was set to 1.65 volts by a ref source and the output bias followed correctly as expected.

However, the inputs now has dc of nearly 1.65V!. So d.c. coupling of signals will be now be affected.

The "virtual earth" points at pin#1 and pin#8 has 1.65V. Was expecting this to be zero under feedback for the inverting amp mode?

Also, if I ground of the inputs for single-ended application, the output common mode gets disturbed and drops to ~1V instead although the ref drive at pin#2 is steady at 1.65V

Thought Vocm affected the outputs only but it seem it affects the input side as well

Please check advise

Thanks