AD8231 vs AD8421 Selection

Question

Dear Support, 
 I am in the design stage to choose an instrumentation amplifier from ADI to amplify a signal before 5V ADC(ADC121s051). The instrumentation amplifier input signal has following parameters: 
 1. The signal has a frequency bandwidth from 100Hz to 150KHz. 
 2. the signal range is between 30uV ~ 30mV(peak-to-peak). 
 I will use 5V supply for the instrumentation amplifier and consider using the maximum gain of 128 from the AD8231 to get the maximum signal swing for the ADC input. 
 I have both AD8231 and AD8421 in my selection candidate list. I prefer to use the AD8231 since its wider frequency bandwidth, rail-to-rail output advantages and direct digital gain control. 
 
 I would like to know: 
 a. what are the primary difference between the AD8231 and AD8421? 
 b. Whether it is a better choice to use AD8231 over the AD8421 for my application, or if I may have some things I miss if I choose the AD8231? 
 Thank you, 
 Lih

GLADION · Accepted Answer

Hi Li0 , 
 
 Good day. The main difference between AD8231 and AD8421 is the gain setting: AD8231 is a programmable gain instrumentation amplifier with software-programmable gains of 1, 2, 4, 8, 16, 32, 64, or 128 while AD8421 is an instrumentation amplifier with external gain settings. 
 The table shows the differences between the specifications of the two in-amp. Highlighted in green are the parameters with better specifications. 
 
 Overall, the AD8421 has a better bandwidth, noise, and slew rate but AD8231 has a lower offset which could be a critical parameter for your design. Looking into your design criteria, both parts can satisfy the bandwidth, but AD8231 excels in terms of the offset parameters. Hence, it is a better choice for your application. 
 
 Can you share with us some other details of your application such as the Vocm and Vref to be use in your configuration? Thank you. Regards, Gilbeys)

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AD8231 vs AD8421 Selection