Greetings!!!

I was doing my homework and I'm not sure about this problem. Is it OK or not? If not, what I'm doing wrong?

 

Greetings!!!

I was doing my homework and I'm not sure about this problem. Is it OK or not? If not, what I'm doing wrong?

I didn't check the entire thing, but I stopped when I got to the point that you said Vo=3V+. This is not correct. The negative feedback path from output to the negative terminal shows a feedback of Vo=2V-, and you are assuming that V+=V-.

 

I didn't check the entire thing, but I stopped when I got to the point that you said Vo=3V+. This is not correct. The negative feedback path from output to the negative terminal shows a feedback of Vo=2V-, and you are assuming that V+=V-.

in my notes i have that in an ideal op amp V+=V-. That's why I'm assuming that 3V-=3V+.

From my KCL@V- i get that V0=2V- + V-. So, Vo=3V-. What I'm doing wrong?

Am I taking the right approach?

 

Then it comes to feedback system it is correct to assume that V+=V- But I did not quite understand why you set Vo=3V
Do you have the correct answer?

 

No, unfortunately I dont have it. I'm getting Vo=3V from the KCL@V-.

 

As I see V-=Vo*50/(50+100)

 

Also use superpostion to find the V+ that is simpler

 

No, unfortunately I dont have it. I'm getting Vo=3V from the KCL@V-.

I'm sorry about my mistake above. I was running out the door to go to work, and didn't think carefully.

Basically, you did the problem right.

You have Vo=3*V+ and Vs=-(4/5)*V+

Your mistake is your last step. If you combine these you should get.

Vo/Vs=-15/4

Time to slap your head, and say "doh"!

 

I'm sorry about my mistake above. I was running out the door to go to work, and didn't think carefully.

Basically, you did the problem right.

You have Vo=3*V+ and Vs=-(4/5)*V+

Your mistake is your last step. If you combine these you should get.

Vo/Vs=-15/4

Time to slap your head, and say "doh"!

DOHHHHHHH!!!!!!!! thanks to you all