• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 47 subscribers
  • Views 271 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Precision Op-amp Training: Lecture 2.2

Siddharth Krishnan
Prodigy 30 points


In Lecture 2.2 on slide 6, it seems as though the calculations of the Voltage error due to the offset voltage and input bias current only accounts for the offset voltage and bias current of the first op-amp in the problem. Why is the bias current and offset voltage for the second op-amp not accounted for? Thank you!

  • 0
    TI__Guru* 93105 points

    Hello Siddharth,

    The example two-stage cascaded amplifier circuit used in Lecture 2.2 uses a simplification regarding the voltage offset and bias currents of the first stage. It is a reasonable simplification because the first stage is operated with a closed-loop gain of 101 V/V, while the second stage has a closed-loop gain of 21 V/V. Since the gain of the first stage is 5x greater than that of the second stage, its offset and bias current errors are the greater portion of the output observed at the output of the second stage where the overall gain is 2121 V/V. You are correct in thinking to be completely accurate that voltage offset and bias current effects of both stages should be considered, but the resulting error from the simplified analysis will be small.

    If you would like a more detailed explanation of the cascaded offset error contributions have a look at the following TI Applications Report, Section 5:

    https://www.ti.com/lit/an/sboa356/sboa356.pdf

    Regards, Thomas

    Precision Amplifiers Applications Engineering