Open Loop Gain

Thread Starter

xn47

Joined May 22, 2007
22
Do you have any easier approach on how to solve the open loop gain of OP-AMP (741 in particular)?
 

bloguetronica

Joined Apr 27, 2007
1,372
Perhaps, negative feedback. Hence we have a closed loop gain, substancially smaller than the open loop gain (since open loop gain is the gain of the op-amp as it is).

But I'm in the dark here, since I'm not sure if you want to decrease gain (what do you mean by "solving the open loop gain"?).
 

Thread Starter

xn47

Joined May 22, 2007
22
by computation. Actually I have finished discussing that topic with my group. Right now, I am currently hooked in computing common mode gain of differential amp using bisection theorem. where; Acm = (-gmRc)/[(1+2gm.REE)(1+1/Beta)]


hmm.. hows that? If its not too much to ask..
 

Thread Starter

xn47

Joined May 22, 2007
22
I have here an attachment of half ckt wherein I transform its current source to its Norton equivalent ckt.. where REE is shunted to the source. How will you get Common mode gain as I state in my last reply..
Thanks..
 

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Ron H

Joined Apr 14, 2005
7,014
I'm not sure that's relevant to a 741. It does not take the output off one collector. It has a current mirror on the output of the differential input stage. The common mode gain is really only a function of how well balanced the current mirror is.
 

Distort10n

Joined Dec 25, 2006
429
Although I am not sure, I would imagine manufacturers use a Venable and sweep across the frequency spectrum to measure open loop gain. The result would be the Bode plot in the datasheet.
I have no idea what the test set up would be.
 
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