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?
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![CS Amplifiers vs. CG Amplifiers [19 points] (a) (b) Fig. P2 All NMOS transistors are biased at saturation region, but only small-signal equivalent circuits are shown in the figures. Each individual NMOS transistor has C2d = 0.1•Cgs, Cdb = Csb = 0.2•Cgs and intrinsic gain gmr0 = 40(>>1). However, the transistor is used as a CS amplifier in Fig. P2(a), but a CG amplifier in Fig. P2(b). Note that the intrinsic output impedance, r8, of the NMOS transistor still exists even though the value of Rsig and RL. have been assigned as rd/2 and re, respectively. For the following questions, please include device capacitances Cb, C2 d, Cb, and Cb if necessary. (a) Find the low frequency gain |vo/vi| of the CS amplifier in Fig. P2(a). (b) Use OCTC method only to find the expression of the time-constant, τ1,cs in terms of Cpd and ro, across the gate and source of the NMOS in Fig. P2(a). (c) Use OCTC method only to find the expression of the time-constant, τ22Cs in terms of Cpd and ro, across the drain and source of the NMOS in Fig. P2(a). (d) Use OCTC method only to find the expression of the time-constant, τ3, cs in terms of C84 and ro, across the drain and gate of the NMOS in Fig. P2(a). (e) Based on (b), (c), and (d), find the expression of 3-dB frequency, fucs in terms of Cp4 and rC, of the CS amplifier. (f) Find the low-frequency gain |v9/vi | of the CG amplifier in Fig. P2(b). (g) Use OCTC method only to find the expression of the time-constant, τ1,CG in terms of Cpd and r6, across the source and gate of the NMOS in Fig. P2(b). (h) Use OCTC method only to find the expression of the time-constant, τ2CG in terms of C84 and ro, across the drain and gate of the NMOS in Fig. P2(b). (i) Based on (g) and (h), find the expression of 3-dB frequency, f fh,co in terms of CBd and r0, of the CG amplifier. (j) Based on (a) and (f), find the ratio of low-frequency gains, |Av,co/Av, cs|. (k) Based on (c) and (i), find the ratio of 3-dB frequencies, fH,co/fH,cs. Result Summary: (a) Av,Cs = (b) τ1,Cs = (c) τ2,Cs = (d) τ3,Cs = (e) fH,CS = (f) Av,CG = (g) τ1,CG = (h) τ2,CG = (i) fH,CG = (j) |Av,CG/Av,CS| = (k) fH,CG/fH,CS =](https://www.doubtrix.com/uploads/editor/0923858882CLzEBqhtpd.jpg)
![CS Amplifiers vs. CG Amplifiers [19 points] (a) (b) Fig. P2 All NMOS transistors are biased at saturation region, but only small-signal equivalent circuits are shown in the figures. Each individual NMOS transistor has C2d = 0.1•Cgs, Cdb = Csb = 0.2•Cgs and intrinsic gain gmr0 = 40(>>1). However, the transistor is used as a CS amplifier in Fig. P2(a), but a CG amplifier in Fig. P2(b). Note that the intrinsic output impedance, r8, of the NMOS transistor still exists even though the value of Rsig and RL. have been assigned as rd/2 and re, respectively. For the following questions, please include device capacitances Cb, C2 d, Cb, and Cb if necessary. (a) Find the low frequency gain |vo/vi| of the CS amplifier in Fig. P2(a). (b) Use OCTC method only to find the expression of the time-constant, τ1,cs in terms of Cpd and ro, across the gate and source of the NMOS in Fig. P2(a). (c) Use OCTC method only to find the expression of the time-constant, τ22Cs in terms of Cpd and ro, across the drain and source of the NMOS in Fig. P2(a). (d) Use OCTC method only to find the expression of the time-constant, τ3, cs in terms of C84 and ro, across the drain and gate of the NMOS in Fig. P2(a). (e) Based on (b), (c), and (d), find the expression of 3-dB frequency, fucs in terms of Cp4 and rC, of the CS amplifier. (f) Find the low-frequency gain |v9/vi | of the CG amplifier in Fig. P2(b). (g) Use OCTC method only to find the expression of the time-constant, τ1,CG in terms of Cpd and r6, across the source and gate of the NMOS in Fig. P2(b). (h) Use OCTC method only to find the expression of the time-constant, τ2CG in terms of C84 and ro, across the drain and gate of the NMOS in Fig. P2(b). (i) Based on (g) and (h), find the expression of 3-dB frequency, f fh,co in terms of CBd and r0, of the CG amplifier. (j) Based on (a) and (f), find the ratio of low-frequency gains, |Av,co/Av, cs|. (k) Based on (c) and (i), find the ratio of 3-dB frequencies, fH,co/fH,cs. Result Summary: (a) Av,Cs = (b) τ1,Cs = (c) τ2,Cs = (d) τ3,Cs = (e) fH,CS = (f) Av,CG = (g) τ1,CG = (h) τ2,CG = (i) fH,CG = (j) |Av,CG/Av,CS| = (k) fH,CG/fH,CS =](https://www.doubtrix.com/uploads/editor/3268471942mKJBTBCcsa.jpg)