Re: miller effect
Miller theory states that :When you have 2 floating nodes with an impedance between them, this impedance can be replaced by 2 impedances to the ground, one at each node .Where Z at node 1=Zoriginal/(1-Av) and Z at node 2=Zoriginal/(1-1/Av) where Av=Vnode1/Vnode2.These formulae are valid for floating nodes and -ve Av or Av<1 .
A special case for capacitors and Av<<-1 (|Av|>>1)e.g common source amplifier, this gate-drain capacitance (C) can be replaced by a cap at i/p of value ≈ |Av|*C which is much larger than the original capacitor which really degrades the frequency response of your amplifier .Note also that Miller's theory can't predict added zeros by this capacitor .