# CL and OL of inverting amplifier

Discussion in 'Homework Help' started by ronybhai, Sep 18, 2012.

1. ### ronybhai Thread Starter Member

Sep 18, 2012
97
0
What is the relationship between the open-loop gain of an op-amp and the closed-loop gain of an inverting amplifier?

Apr 5, 2008
18,696
3,639

Sep 18, 2012
97
0
4. ### ronybhai Thread Starter Member

Sep 18, 2012
97
0
I think this formula can be used for the relationship between CL and OL
Acl=Aol/ (1+B *Aol)

5. ### Papabravo Expert

Feb 24, 2006
11,749
2,483
The closed loop gain is controlled by the external components and the open loop gain does not enter into the calculation.

ronybhai likes this.
6. ### ronybhai Thread Starter Member

Sep 18, 2012
97
0
Open loop doesnt enter into what calculation?
Can you verify if the formula I posted above is correct?
Thanks

7. ### Ron H AAC Fanatic!

Apr 14, 2005
7,049
674
Suppose Aol=100k, and the feedback ratio is .001. You actual gain would be ≈1% lower than the value calculated from the feedback resistor ratio. Open loop gain can usually be ignored, but you need to be aware that it is finite.

8. ### Papabravo Expert

Feb 24, 2006
11,749
2,483
That is true, but we seldom have a closed loop gain that is closer to the open loop gain than say four orders of magnitude. This is like saying I write all my answers to 9 significant figures because I like to be precise.

One of the great benefits of reducing the gain by closing the loop is the corresponding increase in bandwidth.

9. ### Ron H AAC Fanatic!

Apr 14, 2005
7,049
674
"Seldom" is the key word here. This is precisely why I said