AD8428 Gain.

Question

hey there! 
 I have some questions and would appreciate your help:

I want to use the AD8428 IC to amplify a 0.2 mVp-p signal at a frequency of 32 kHz. Is this IC capable of amplifying my input signal as specified?

I simulated this IC in LTSpice, but the output is not as expected. The gain I&rsquo;m seeing is around 32-37 V/V, even though the AD8428 is supposed to have a fixed gain of 2000. Could you please help me understand why my circuit in LTSpice isn't producing the expected gain of 2000? 
 
 and how to remove offset , because sometimes my output didn't start from 0 in graph. 
 
 Any suggestions on why I&rsquo;m not getting the expected output would be greatly appreciated.

GLADION · Answer

Hi OpAmp , 
 Good day. The AD8428 should be able to work with your configuration and input setup based on the diamond plot tool ( https://tools.analog.com/en/diamond/#difL=-0.0001&difR=0.0001&difSl=-0.0001&gain=2000&l=0&pr=AD8428&r=0&sl=0&tab=1&ty=2&vn=-5&vp=5&vr=0 ). 
 The AD8428 has a fixed gain of 2000. However, the AD8428 gain can be configured by attaching a resistor across the +FIL and -FIL pins. Based on the schematic you shared, a 15 ohms resistor across the filter pins configured the AD8428 gain to around 5 V/V (You can refer to "Setting the Amplifier to Different Gains" of the datasheet). From the LTSpice simulation, the output is around 500 uV for an input of 0.1 mV which would suggest a gain of 5 and coincides with the gain calculated. If you want to configure the AD8428 for a gain of 2000, you should leave the +FIL and -FIL open. Lastly, to address the issue on the offset, you can counteract it by applying a DC voltage of 49.9 mV at the output of AD8428. But I would suggest that you consider the offset since this is modeled based on the part's specification. 
 Here is my simulation for reference: 
 Hope this helps. 
 
 Thank you. 
 Regards, Gilbeys

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AD8428 Gain.

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