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Questions about Ti precision lab-SAR-Quiz: Driving a SAR ADC with a Fully Differential Amplifier

Dear Precision lab,

Could someone answer my follow-up questions for the first question regarding the linear input range in this thread I posted before? 

https://e2e.ti.com/support/amplifiers/f/14/p/718921/2662019?tisearch=e2e-sitesearch&keymatch=%20user:311920#2662019  

1. When we discussing the input linear range of the opamp, we actually only consider the common mode voltage range, such as in first attachment, and also in your opamp video the second attachment.  We defined the opamp input range as the common mode voltage range see attachment 2. All this discussion we did not consider the actual signal applied to this common mode to be amplified. Is this because they are small signals? 

2. But if we have the situation that the input signal  is large ("the signal " refers to the signal applied on the common mode voltage) such as the case in attachment 3, the FDA input signal is the same order as the common mode 2.5V, if we want to calculate input linear range, whether we should consider the range of the "signal" + common mode voltage? In that case, the input voltage range should not be just the input common mode voltage as shown in the attachment 2?

PS: The attachment 1 is from  TI precision lab SAR adc  lecture 2-2 determine ADC linear range using opamp P3

The attachment 2 is from TI precision lab opamp lecture input output limitation -1  P4

The attachment 3 is from TI precision lab SAR lecture 2-5 determine ADC linear range using FDA P7.

Thank you very much,

B. Fan.

  • B. Fan,

    Sorry for the long delay. I answered this on the other thread. I will close this re-post soon. I'm glad to help with any questions, and again, sorry for the delay.