Is it possible to get gain of 1000 in a LM324 or OP07 practically? If not why? What gain can an OPAMP provide maximum? Why this restriction?
Hi Lahari, there is no theoretical restriction - but, certainly, a practical one.
An opamp could - theoretically - be operated without feedback at its maximum gain - provided that there is no offset !
But this never can be ensured in practice.
Therefore, negative feedback is necessary to bias the device in its linear region - more or less independent on offset effects.
In addition, negative feedback offers some other important advantages:
* less sensitivity to active tolerances (open-lop gain, temperature and offset effects)
* less sensitive to supply voltage variations
* less distortions (better THD)
* larger bandwidth
* smaller output resistance (better voltage source properties)
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* Disadvantage: Increased tendency to oscillations (less phase margin).
* Comment: The reduced gain due to negative feedback is no real "disadvantage", because this reduction is desired and leeds to less sensitivity of the final gain value to open-loop gain variations (uncertainty).
W.