Dual supply and Ref voltage

Question

Hello, 
 
 I am planning to configure the circuit as shown in the diagram. The input voltage ranges from 0V to 2V, and the output voltage ranges from -1V to +1V. R1 in the diagram is intended to be a variable resistor (0~20K). Are there any issues with the configuration of AD8421 and OP1177 in this setup? 
 Thank you.

Arsol · Accepted Answer

Hi jingum2 
 Thank you for contacting us and sharing your questions with the team. 
 To give the correct recommendation, I would like to confirm these data as I understand them in your schematic diagram. 
 
 Target applications is Current Sensing through 1Kohm Rsense (R4) 
 Supply values: +Vs =5V and -Vs = -3.3V 
 Vref= 1.03125V using a -3.3V to a res divider (R3//R2), and to buffer (OP1177). 
 Intended input voltage range = 0 to 2V 
 Rg = 320, Gain is approximately = 32 
 
 Basing the results from the Instrumentation Amplifier Diamond Plot Tool, the conditions above will work. If you want to try other combinations and conditions, I recommend using the diamond plot tool: https://tools.analog.com/en/diamond/#difL=0&difR=0.00005&difSl=0&gain=32&l=0&pr=AD8421&r=2&sl=0&tab=1&ty=1&vn=-3.3&vp=5&vr=1.031 
 
 Here are some reference materials for your guidance: 
 https://www.analog.com/en/education/education-library/videos/4605020056001.html 
 https://www.analog.com/en/app-notes/an-1401.html 
 
 Please contact the team if you have additional questions. 
 Regards,)

Arsol · Answer

Hi jingum2, 
 In your 1st question; there will be no issue as long as your Vref value is within the recommended range (min = -Vs to max = +Vs) and if you intended to use the -1V. 
 
 I don't know what kind of noise you are referring into the output. For us to give the proper suggestions, Can you please expound further the details of this noise? 
 Regards,

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