Please help me with issues about instrumentation amplifier AD8553

Question

Hi, I'm using AD8553 in my project. 
 Below is my schematic. 
 
 And here are input and output: 
 
 Could anyone help me to resolve this issue? 
 Thanks.

Arsol · Accepted Answer

Hi CoKa 
 Thank you for reaching out. We are validating your inquiries; we will need additional information from your circuit design before anything else. May I know what applications you intend to use for the two (2) AD8533 ( U10 and U13 )? If this circuit was designed to drive an ADC? 
 
 Can you expound further on the table that you provided and your design requirements? i.e. target Gain , expected output , Input range , etc&hellip; I see you are using two (2) types of input: one is pure DC and another is AC ( is this a sinusoidal wave w/ frequency of 1kHz ?, is there any DC offsets for the AC input? ). Then, please provide a scope shot on Pin2(VINP ), Pin9(VINN ), Pin7(VREF ), and Pin4(VO) for the two (2) input conditions . 
 
 I suggest we run several diagnostics on your design; Hence, will use the existing U13 circuit and please do the following: 
 
 Isolate this circuit by disconnecting other circuitries connecting to C39 or Ch4 node. 
 Remove R74 and R75 . 
 Change CH4_P input from +25Vdc to 3.6Vdc . 
 Check if the Vout is the same = 4.23V . 
 Lower Down your CH4_P input from 0.8 to 3.5Vdc 
 Check if the Vout will be similar to CH4_P input. 
 
 Please let me know if this helps. 
 Regads, 
 Arsol)

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Please help me with issues about instrumentation amplifier AD8553