AD8557 I want to measure current at a 0.1 ohm with one end to a load and Vcc and the other to ground. The voltage in the (-)input is in the order of 3 mV or less but I cannot amplify it

Question

AD8557 I want to measure current at a 0.1 ohm with one end to a load and Vcc and the other to ground. The voltage in the VNeg is in the order of 3 mV or less but I cannot amplify it. 
 
 When I add another resistor in series with the 0.1 Ohm resistor in the low side raising the VNeg input it, works Ok 
 
 So what is the minimum voltage I need in (-)input 
 
 Thanks

GLADION · Accepted Answer

Hi TomasMDZ , 
 Good day. For a single supply operation with Vdd=5.0V and Vss=0V, the allowable input voltage range is 0.6V to 3.8V. If the Vneg input is less than 0.6V, It seems that the part is not operating in the linear region. 
 
 I think that is also the reason why it works when you raise the Vneg input. Thank you. Regards, Gilbeys)

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SLA Closed. Met after 67 hours	AdrianF	Closed

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AD8557 I want to measure current at a 0.1 ohm with one end to a load and Vcc and the other to ground. The voltage in the (-)input is in the order of 3 mV or less but I cannot amplify it

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