(a(i))[4]
Using the properties of an ideal op-amp, explain why point P is called a virtual earth.
(a(ii))[4]
Derive an expression for the gain of the amplifier circuit in terms of $R_1$ and $R_2$.
(b)[3]
In Fig. 7.1, the ratio $\frac{R_2}{R_1}$ is 4.5. The input potential $V_{IN}$ is shown as a function of time $t$ in Fig. 7.2. On Fig. 7.2, indicate how the output potential $V_{OUT}$ changes with time $t$.