# Analysing a circuit with an inverting amplifier

#### MāiợỖoŞh XĐ

Joined Dec 12, 2015
3
As I finished my bachelor's a while ago I had some trouble analysing this circuit. I am aware of Kirchhoff's law.

Given here is that the absolute value of Av is zero, which leads, as far as I understand, to a short circuit on Zout and Yin.

Required is Vout. As far as I understand there are two equations, first:
Vout,n = Iout * Zl
Second:
Iout(Zg+R1+R2+Zl) = Vg-Vn,1 + Vn,2

and we are supposed to substitute the second eq. in the first to solve for Vout.

However, the solution had another way of describing Vout which is:

Vout = -IR2 + Vn,2

Can some one explain this misunderstanding?

#### MisterBill2

Joined Jan 23, 2018
18,425
Why fight with current for solving an op-amp question, when using voltage works so much more simply?? What is the benefit??
I graduated 50 years ago and have not used the current math for any op-amp calculations during that time since. In addition, I have been able to avoid including those "Norton" current mode op-amps as well. And what value is a device with a gain of "ZERO"!!!

#### MāiợỖoŞh XĐ

Joined Dec 12, 2015
3
Why fight with current for solving an op-amp question, when using voltage works so much more simply?? What is the benefit??
I graduated 50 years ago and have not used the current math for any op-amp calculations during that time since. In addition, I have been able to avoid including those "Norton" current mode op-amps as well. And what value is a device with a gain of "ZERO"!!!
I don't know why you are yelling?
It is a master degree course.
So maybe we have to ask the professor putting the exams why he is asking such question?!

#### Papabravo

Joined Feb 24, 2006
21,222
Chill. Yelling would be the whole post in capital letters. I count one word of four capital letters. That is hardly yelling, just emphasis.

#### MāiợỖoŞh XĐ

Joined Dec 12, 2015
3
As I finished my bachelor's a while ago I had some trouble analysing this circuit. I am aware of Kirchhoff's law.

Given here is that the absolute value of Av is zero, which leads, as far as I understand, to a short circuit on Zout and Yin.

Required is Vout. As far as I understand there are two equations, first:
Vout,n = Iout * Zl
Second:
Iout(Zg+R1+R2+Zl) = Vg-Vn,1 + Vn,2

and we are supposed to substitute the second eq. in the first to solve for Vout.

However, the solution had another way of describing Vout which is:

Vout = -IR2 + Vn,2

Can some one explain this misunderstanding?