4. A common-source amplifier is based by R₁ and R2 as shown below. Assume VTHN= |VTHP|= 0.6 V, AN=Ap= 0.05 V-¹, and ₂Cox= 200 μA/V² and upCox= 100 μA/V² (a) Assume Ibias = 0.1 mA. Determine R₁ and R₂ to set Vx as 1 V. Also, determine the drain current ID. Neglect channel-length modulation in the calculation. (b) Based on the obtained Ip in (a). Design Rp to achieve the maximum allow gain of this amplifier. Also, determine the small-signal gain Vout/Vin under this condition. (c) If RD is replaced by a PMOS (W/L= 400) as an active load (biased in the saturation region), plot the small-signal model and determine the small-signal gain of the amplifier. Assume ID is kept the same as in (a). How about if the PMOS is replaced by an idea current source of ID? Determine the small-signal gain under this condition. VDD= 2.5 V R₁ bias Vin R₂ www Vx Ro D Vout W/L= 200 Vm R₁ bias R₂ VDD= 2.5 V 11 Vx W/L= 400 out W/L= 200