PGA112/113 offset error

David Chance

Other Parts Discussed in Thread: PGA113

Hi there,

http://www.ti.com/lit/ds/symlink/pga113.pdf

On page 3, it says, the input offset voltage can be +/-100uV maximum

I am not sure how to interpret this info.

If we have AVdd=DVdd=3.3V, Vref=Vin=0.9V, what will be maximum offset error on the output? 100uV regardless the gain?

Thanks for your time!

over 10 years ago

0 John Caldwell over 10 years ago

TI__Genius 12325 points

This specification is input referred, meaning it must be multiplied by the gain of the amplifier to determine what the offset will be at the output. For example, for an input offset voltage of 100uV, if the PGA113 was configured in a gain of 10, the offset measured at the output would be 1mV (100uV * 10 = 1mV).

0 David Chance over 10 years ago in reply to John Caldwell

Genius 4760 points

So, even I short the Vin to Vref, PGA113 can still have maximum 100uV offset error

if I use gain of 200, the maximum output offset error is 100uV*200=20000uV or 20mV

Am I correct?

0 John Caldwell over 10 years ago in reply to David Chance

TI__Genius 12325 points

This is only the error due to the input offset voltage. Other factors will also contribute an error voltage such as the common-mode rejection and power supply rejection and input/output swing limitations. This is a good blog post about calculating the offset voltage which results for these additional factors: http://e2e.ti.com/blogs_/b/precisiondesignshub/archive/2013/08/05/will-the-real-vos-please-stand-up.aspx

Amplifiers

Amplifiers forum

PGA112/113 offset error