# Evaluating 741 op amp sensitivity to loading in non-inverting and summing op amp circuits

I am doing lab preparation but I am not sure how to evaluate 741 amplifier sensitivity to loading based on my non-inverting circuit with a gain of 21 and my summing circuit with a gain of 55. I know that I should use you find gain for R1 and gain for R2, and then find the ratio of the relative changes. But I am not quite sure how to implement this.

(delta G/G ) / (delta A / A)

note: for non-inverting circuit my R1= 22Kohm, R2= 1.2kohm and for summing circuit R1=82kohm, R2=1.5kohm

Any help will be so very much appreciated.

Summing inverting amplifier:

Non-inverting amplifier:

• I understand you're a student and may be required to use 741 for this lab, but here's some good supplementary reading about the practical limitations of that opamp: electronics.stackexchange.com/questions/304521/… – MarkU Nov 2 '18 at 22:46
• Noninverting gain is 1+(Rfeedback/Rinput), right? So noninverting gain of 21V/V requires a feedback ratio of 20:1, not 22:1. – MarkU Nov 2 '18 at 22:51
• Thank you @MarkU , I will give that a read, and I had to use 22:1.2 due to what was available to me at my uni lab! I understand I can re-organise with some series to get the exact ratio however for the purpose of this task 22:1.2 was close enough -apologies I edited it I did write 1 instead of 1.2 by accident. – Ida Mora Nov 3 '18 at 0:47
• Ida Mora - what is really your question? Loading effects? Do you really want to take the tiny output resistance of the opamp into consideration? Or the limited output current capabilities? – LvW Nov 3 '18 at 10:02
• @LvW I understand that it is very small however this is a specific question I have been asked by my lecturer that I am not sure at all about how to implement. The exact question is: What is (741) amplifier sensitivity to loading. – Ida Mora Nov 3 '18 at 16:17