(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

We did a lab analyzing this inverting, negative feedback circuit for a 741 op-amp:

We measured the closed-loop gain and phase shift of the signal for several values of the input frequency with [itex]R_2/R1=1000[/itex],[itex]R_2/R1=100[/itex] and [itex]R_2/R_1=10[/itex]. The gain curves all looked like horizontal straight lines for low frequencies, and then some sort logarithmic decrease for larger frequencies. The phase shift curves looked sort of similar; they all started with π radian shift for low frequencies with some sort of logarithmic decrease before leveling off slightly near the end.

The problem is, I have no idea what the theory is behind the shape of these curves. We know that the ideal case is [itex] G = -\frac{R_2}{R1}[/itex], but the max values of the measured gain weren't even close to that. If someone could point me in the direction of a source that deals with the theory (equations) for this circuit's frequency response, that would be great.

2. Relevant equations

Exactly what I need to know.

3. The attempt at a solution

I did find one pretty good paper here:

http://coe.uncc.edu/~dlsharer/ETEE3212WebCT/SectionH/H7.pdf

On page 4 it gives:

[tex]G = \frac{G_o}{1 + s/{\omega_o} + {G_o}{\gamma}}[/tex]

But I don't think it's for exactly the same circuit as I have, and it doesn't have any equations about phase shifts.

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# Op-Amp Frequency Response Theory

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