Differential Op Amp Gain Problem

  • Thread starter caprice24
  • Start date
3
0
Hi,

I have a problem I am trying to work out on simple Op Amps gain, and I am having trouble trying to prove what the gain is. I know what the gain is supposed to be (see below), but I am stumped as to how to actually go about proving it. When I try to setup the Kirchoff node equations I get a really ugly polynomial.

I can put the design into a spice deck and prove it, but I want to understand the design from an analytical point of view.

Gain = 2*R2/R1 * (1 + R2/Rg)(V2-V1) (GAIN FOR THE OP AMP in the attached jpg file)

Now looking at the above equation it is obvious if you eliminate resistor Rg, the equation becomes a simple differential amplifier gain, which I can easily solve and prove. However when you add the positive feedback from the output, you get a different Beta for the loop gain that is hard to figure out.

Nick
 

Attachments

anorlunda

Mentor
Insights Author
Gold Member
7,568
4,276
That makes no sense at all. R2 is in parallel with RG. So whether or not there is positive feedback, can not depend on the value of RG.
 

Want to reply to this thread?

"Differential Op Amp Gain Problem" You must log in or register to reply here.

Related Threads for: Differential Op Amp Gain Problem

  • Posted
2 3
Replies
62
Views
8K
  • Posted
Replies
7
Views
6K
  • Posted
Replies
2
Views
730
Replies
37
Views
8K
Replies
7
Views
2K
Replies
2
Views
1K
Replies
9
Views
41K
Replies
8
Views
685

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving

Hot Threads

Top