Exercise 7.6 Multiple configurations - which is stable??

The figure below shows four circuits with (identical) opamps; these are marked a), b), c) and d).

The Bode plot of the voltage gain $A_{\mathit{opamp}}(\mathit{j\omega })$ of the opamps is shown in the next figure. The input impedance of the opamp is infinite, its output impedance is $0\mathrm{\Omega }$.

a)

From the Bode plot, derive/formulate a parametric equation for $A_{\mathit{opamp}}(\mathit{j\omega })$ of the opamps. Please use this equation for voltage gain — as long as possible — in the derivations below to retain readable parametric equations.

b)

We want the amplifier circuits to operate stable with a gain of $A_v=+10$ in the frequency range of $0\dots 10\mathit{kHz}$. Which of the configurations a through d has the largest phase margin?

c)

Determine the phase and gain margin for the circuit of in c) in the figure.

d)

Derive an expression for the output impedance of the circuit schemtic marked c) in the figure. Do this for the frequency domain of $0\dots 10$ kHz. Estimate first which pole(s) can be neglected for this question.