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Vref Question with Single Supply

Category: Datasheet/Specs
Product Number: AD8553

I want to use the AD8553 with a single supply of 5Vdc.  My input swings from 0.06 to 0.131Vdc. Nothing Negative or below ground.  I don't quite understand the datasheet of why I can't connect Vref to ground.  The datasheet says for single supply applications tie this to a voltage between ground and Vcc and suggest this is 2.5Vdc or use a reference.  I would like to apply gain and get as much usable range on Vout as possible.  Maybe the max Vout of 4.8 (0.131 x ~36 for gain).  Couldn't I just set Vref to ground(to save using a precision reference) or 0.1Vdc at a minimum (with a reference to achieve max usable range on Vout)?   This is a low frequency application and the source is low impedance ~100ohms.  I do see the lower Vout range (Vsat low maybe?) is 0.075Vdc.  Thank you for your help.

Top Replies

  • Hello  ,

    Unfortunately having the Vref directly tied to ground at single supply operation will degrade its high CMR performance. 

    Ideally from Figure 30 in the datasheet, Vref to ground is possible…

    •  Analog Employees 
    •  Super User 
    Feb 12, 2024 in reply to Gary1001 +1 verified

    Hi  

    Thank you for sharing your inquiries.

    For the follow-up question regarding CMR performance vs Vref, the CMR parameter is mostly driven by how your offset voltage changes with respect to your…

    •  Analog Employees 
    •  Super User 
    Feb 14, 2024 in reply to Gary1001 +1 verified

    Hi  

    There will be no disadvantage of increasing the reference level; but for it to work properly please refer to the product datasheet; specifically table 1 on page 3: https://www.analog.com/media…