In general, the miller theorem is used for converting any circuit having configuration of figure 2.48 (a) to another configuration shown in figure 2.48 (b)
If Z is the impedance connected between two nodes, node 1 and node 2, it can be replaced by the two impedances Z1 and Z2 ; Where Z1 is connected between node 1 and ground and Z2 is connected between node 2 and ground.
Proof Of Miller’s Theorem
Miller’s theorem states that, the effect of resistance Z on the input circuit is a ratio of input voltage Vi to the current I which flows from the input to the output.
Z1 = V1 / I