Question

VOD R1 R3 ie + ij Vop=10V 2=0.01 V-1 for ac analysis only Hp Cox(W/L)p=250uA/V2 un Cox(W/L)n=5004A/V2 | Vtpl= |Vtn/=1.2V RL=3k92 Ri=10022 R1=71622 R2=75692 C1=2uF C2=5uF C3=3uF Cgs=12pF Cgd=8pF 7 03 ROUT R. V. Ri C1 RIN R2 R4 C2 A. (12 pts) Calculate values for R3 and R4 for the amplifier circuit given a Q point of (1.2mA, 5.5V). R3 R4 B. (13 pts) Calculate a value for the estimate of the high cutoff frequency of the amplifier. Include ro. For full credit, include the circuit analysis to justify your answer. C. (4 pts) Sometimes, we can assume r, is infinite when doing ac analysis. Recalculate your answer in part B with infinite ro. How did your answer change? Were you surprised at the result? Comment. D. (4 pts) If you wanted to increase the bandwidth in the answer from part B by 20-30%, which resistor(s) would change without having a significant impact on the Q-point? i.e. which resistors have the greatest influence on the high cutoff frequency. (circle resistors) Briefly justify your answer. Ri R1 R2 R3 R4 RL

Answer 1

D C performing Analysis VOPSION 0 R3 Rth - RollR2 - 411175 = 36.4 fland R4 + Vth = 5.136V R2 wth = X VDO 11 75 x 10 75 + 7 Ret R2 Vth 5.136 V Given @-point (1.2mA, 5.5.v) x An Coxx V+) 2 ID Cox * ( (W) x (vgs 1 x 500x100x cugs.1.233 X 1.2410-3 S - 50136 V (as IG 20 3 • 39 v vgs NG 50136 - 3:39 NS - = 1.745 V 1.745 R4 •2 R4 = 10454 kurz Vs ID

Given Vos : 5.5V Voo CR3+R4 ) to - Vos 10-5.5 CRER4 ) x 1-2x10-3 R3 t R 4 -3.75 kan 2.296 K 12 TRB B) performing Ас Analysis, Applying mino Theoren ro AID = 83.33 koh 2 0.01 X 102 Ri + Roll R2 ulo vos Re co gm vgs См HO 5 2x Tox Mn Coxx = 1.095 mA from xx(@) gm = √ 2 x 102x10-3x500x10-6 gom mA/V cgs Av=71.095 * (R3 || Rell no) Av 2-1.095 x ( 3 || 2-2 21 296|| 8 3.33) cm = 12 + (204022) 88 + (1 - Av) cgd. см. AV ? -1.4022 31.218 pr

Cm 1 OTKN Resistance seen seen by Roll Rallri Rm 7111451100100 fr $4 2 AXO.1X 1000 X 31.218 X10-12 2x X CM X RM fr I 50.98 MHZ H c) Now r - do when & / Av= - Im CR311 Re) JI -1.0.95 Av -1.424 CM = cgs st (1- Av) Caled 1 2 + 2.42448 Rm z ootke agd : 31:393 PF - 27 X Oud X 1000 x 310 393 x 10-12 fr fr 50.697 MHZ as ro is in Therefore Av mestu *H pedues slightly Infinite Av redu Increases slightly thus gnereases Slightly Hence Slightly См Hence fH decreases

10 1 Band width depends on Higher cut-off frequency .: fH 2a Cox frill R2Il Ri R2 and Ri has in influnce Higher t-off frequency ince on Thus Ri Il the His Cut-