[circuit theory] Transfer function of feedback network

Status
Not open for further replies.
M

melkord

Full Member level 3
Joined
May 18, 2018
Messages
151
Helped
0
Reputation
0
Reaction score
1
Trophy points
18
Activity points
1,772
In the system with negative feedback, what is described by G(s) actually? is it G(s)=A(s)/Y(s) ?

If I want to derive Y(s)/X(s), is it a correct way to derive G(s)=A(s)/Y(s) and then I can plug it in to the equation (8.2)?

With simple resistor as feedback, I usually derive the transfer function directly.
But right now, I have a quite complicated feedback network with some frequency-dependent components.
That's why I want to derive G(s) first.




 

Attachments

  • 1639570082378.png
    138.3 KB · Views: 136

Sort by date Sort by votes

Attachments

  • AN154.pdf
    843.2 KB · Views: 170
Last edited:
Upvote 0 Downvote
danadakk said:
Just derive the G(s) element expression, and plug that
into 8.2, just as you do for H(s).
Click to expand...

sorry it is a bit unclear for me.
I think I should derive G(s)=A(s)/Y(s) when the feedback network is detached from the feedforward. Is this correct?


I will check your links. Thanks
 

Upvote 0 Downvote
Yes, you treat G(s) as a stand alone network with an input
and output. But dont use Y(s) as input because that would make
it a f( G(s), X(s), Y(s) ). So make input Z(s), output A(s), and then
solve for is T(s) = A(s) / Z(s) and plug that into the general T(s)
for the overall problem.

Regards, Dana.
 
Upvote 0 Downvote
I wonder what you mean with "derive G(s)"? The feedback factor is intentionally chosen in the design process.
 

Upvote 0 Downvote
You are stating in post #1:
I have a quite complicated feedback network with some frequency-dependent components.
That's why I want to derive G(s) first.
Click to expand...
In this case, G(s) will be described by a rational function with numerator and denominator coefficients (zeros and poles). Consider that the "detached" feedback network must be loaded similarly to the final circuit.
 

Upvote 0 Downvote

Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…