For the differential amplifier shown here, VDD = VSS = 5 V, the load resistance R = 80 kΩ. The biasing current is provided by a MOSFET current mirror, IREF = 250 μA. For MOSFETs, Kn1,2,8,9 = 0.25 mA/V2, Kp3,4 = 0.20 mA/V2, VTN = VTP = 1.0 V, λ1−4 = 0.01 V−1. Channel length modulation is neglected for M8,9, i.e. λ8,9 = 0. Here VDS is neglected in the calculation of ro. (a) Find the Q points of M1, M3, M8 and M9. (24 pts) (b) Find the differential mode voltage gain and the output resistance. (12 pts) (c) Find the input resistances for the differential mode and common mode. (12 pts)
For the amplifier in the below, draw its AC equivalent circuits (half circuits for the 1st stage) for (1) (6 pts) AC common mode, (2) (6 pts) AC differential mode, (3) (18 pts) and express Avt1, Avt2 and Avt3 (in terms of gm, ro, currents and resistances) for the differential mode. The current sources have AC resistances of R1, R2 and R3, respectively. (4) (6pts) Which MOSFETs determine the CMRR of the whole circuit?
Consider the ac equivalent circuit in Figure P6.73. The transistor parameters are β1 = 120, β2 = 80, VA1 = VA2 = ∞, and ICQ1 = ICQ2 = 1 mA. (a) Find the small-signal voltage gain Av1 = Vo1/Vi. (b) Determine the small-signal voltage gain Av2= Vo2/Vo1. (c) Find the overall small-signal voltage gain Av = Vo2/Vi.