Small signal gain and impedance a) Show the small-signal model to find Vout/Vin. M1, M2, M3 has an infinite output impedance (rds = infinite). Vb is a bias voltage. Assume all saturated. (5pt) b) Find the small signal gain defined by Vout/vin. (10pt) c) Find the small signal output impedance (5pt). d) Find the small signal input impedance (5pt).