Open loop transfer function help

[axe34]

Homework Statement

[/B]
I need to work out the open loop transfer function of the above. I've drawn it on word so it's not great; the + and - represent a summing junction.

Homework Equations

Everywhere I read, I find a different definition of open loop transfer function. I see G*H is an oft used equation but I'm not sure...[/B]

The Attempt at a Solution

None!

 

[LvW]

Your drawing contains a loop of several blocks, correct?
Do you really have no idea which elements/blocks determine the transfer function of the loop under open conditions?

 

[axe34]

No I do not.

 

[axe34]

KpKaGcGp / (n + KpkaGcGp) is the answer supposedly but I don't know how this was derived.

 

[LvW]

axe34 - no, it is not correct.
Here is the procedure for measureing/simulating the gain of the open loop.
You have nothing to do than to open the loop (at any place you like), to inject a test signal and to find the output at the other side of the opening.
And this procedure gives you the method also for calculating the gain within the complete loop. It is easier as you might think - and it is quite logical!.