Question

QUESTION 4 For the circuit in the figure, 8m1 - 8m2 8ms - 833 MA/V, 8m3 = 8m4 = 599 JA/V, ro1 = ro2 = '05 - 452 kq, l'o3 = '04 = 132 k2, what is the common mode rejection ratio in V/V? (0 decimal places, within 100) MUM OVO VGM Move VE HIM

Answer 1

Given Data : 9m. = 9m2 = 9m5 = 833 Adv 9m 3 = 9m4 - 599 MAlv, Yo - Yo2 = V05 - 452 km Yo3= You = 132 kr Finding common mode voltage gaios AC- small signal equivalent circuit Common mode for r ? 104 tvo @ Vcm UA2 ro5 105 . if common input Vom is applied then Current through both transistors become same aso we can split ros among two MOSFETs as below

rou Ivo 6 vem 1 2ros 2705 I I The above Mosfets acts as Sommon source Ccs) Amplifiers with unbypassed Source resistance 2805. : Vo - -gm, (roull roa) Vem It gm, (2005) in common mode gain Acm = -9m2 (roull ros) 1+9m2 ( 2005) -8334 ( 132k || 452k) (+8334 (2x452K) 132k11 452le a 132x452 132 +452 2 102 .16ks

Acm = - 833 x1o Os 102.16x103 1+ 833 x17%(2x452x10%) Acm = -0.1128 | finding differential mode voltage gain. In differential mode ros-resistor is neglected and the small signal equivalent is rou vo Alam Vo = -9m Croull rou) 2 = -833 41 ( 132k11452b) -833 x106x 102.16x cot3 I Aam=-42.549

common modo rejection Ratio (CMRR) CMRR = |Admi | Acmi 42.549 0.1128 CMRR = 377.21 v/v