buddypoor wrote on Nov 7th, 2011, 3:37am:Hi Alexander,
I suppose you are somewhat more familiar with the secrets of the english language than I am. Thus, I agree with you.
However, for a reasonable design (that makes sense) and for a second opamp with a GBW that is not much larger than that of the 1st opamp there will be a 2nd pole in the active region of the resulting opamp combination.
Don`t forget, the composite opamp should have better properties (more gain for higher frequencies) if compared with a single opamp. Otherwise the whole combination makes no sense. Of course, I can give the 2nd opamp with feedback a gain of 0 or perhaps 6 dB. But, where is the improvement?
Therefore,.....
Well first of all, the second opamp might have other features than gain. Say for example a good driving capability or so. You could mix a low noise opamp with a low distortion opamp in this way.
But assuming that the second opamp would purely be used for gain, why placing the local feedback at all? To me it would seem better to get rid of that local feedback (find a way of preserving the negative sign), and use some decent frequency compensation, e.g. placing a capacitor in parallel with the resistor in the fb network (i.e. placing a zero in the fb). Much more efficient, imho.
Thx for the info. I will take a look at it some time. =)