Hi,
But say i have 3V in the non-inverting terminal and 2V in the inverting terminal and gain is 4. So at first (3-2) *4 = 4V. So now this 4V output is given to the non-inverting terminal.
So next it will be (3-4) * 4 = -4. (-4 now to the non inverting terminal) and so
Next it will be (3-(-4))*4 = 28V. And say out power supply can supply only to 15V So now output will be 15V and will be fed back. And so (3-15)*4 =-48V... This example keeps changing the output. How can i bring it to a stable state like in the first example shown.
What you describe is the problem with digital regulation loops.
You are thinking in "steps". Steps in time and steps in voltage.
But this is not true with analog systems.
When IN+ = 3V, IN- = 2V and gain = 4 then you imagine the output jumps from 2V (because output = IN-) to 4V.
But it doesn´t jump. It moves. Every OPAMP has a limited slew rate. For your example let´s assume it is 1V/us.
so imagine 10 ns of time later..
(now you may say: this 10ns is a step, too! True. But while the voltage moves continously, not in steps, we just take a snapshot 10ns later of the voltage to see what happens. You may vary the timng of your snapshots... but the result will be the same..)
Within the 10ns and a slew rate of 1V/us the voltage moves 0.01V
Now the voltages are 3V, 2.01V --> (tries to target) 3.96V
10ns later: 3V, 2.02V --> 3.92V
10ns later: 3V, 2.03V --> 3.88V
and so on...
after a while:3V, 2.38V --> 2.48V
10ns later: 3V, 2.39V --> 2.44V
10ns later: 3V, 2.40V --> 2.40V (hit the target. Stable)
(This is a simplified view!)
Klaus