Question

Look at the circuit below and try not to freak out!). Assume all transistors are in the active mode. You must now decide whether to include or neglect the Early effect (r.) in your model for each transistor - use the rules we established in class (don't just neglect it every time!). & Voc ¢ Voc a VoR Toetan SRE Rino R Fig 2 a) [3 points] Draw a small-signal model for this circuit (this may take a full page - leave yourself plenty of room). Be sure to label each small-signal parameter carefully (e.g. gml for Q1, Vbe3 for Q3, etc...) b) [4 points) Based on your model, find expressions (do not calculate anything) for Rin, Rina, Rink and Rout in terms of the resistances and small-signal parameters of the transistors. c) [3 points] Find expressions for the voltage gains vx/vs, Vy/V, and v/vy in terms of the resistances and small-signal parameters of the transistors.

Answer 1

solution Given circuit diagram is Trec vce FR62 I I Rey nad Ring ty 'Raul a) I'm neglected I'm neglected the Early Effect "r" small signal model for Each transistor ~ ~ ~ 7 agmebe, & RC 77 je toren + zrez @gm, ube. Vhes Rey bey + Rollosa be rea Ez Vbey frey SREY for small signal Analysis Desources are grounded sharled. Egrounded]

amarbey Digm, Vbez okres bez th the gm ubey & Rey BE31 27 - an bei " Pina 70s Tubey & rey ovoul Tip PGIRR valve, Ring to Z RE4 Rin 1=1 ms rezon Xez: на 5 Хеч гарч Pin= (R. (18) se [Pina. -8e3 + b31/6444 Qey]x] > Rrest (espezil feu treball Ring: Refent Rey Rout = Reallrey If yout want you can replace Tres gm' in Rin, Rin A, Ring, Rout small signal resistana with gn's.

18 Pin= (Ruilles | Bom kina = pa tungt (Pes 11 ( guru Pey] py] Pin B = By (1 ou + REUS Rout - Reallogmu 74 in for finding vyro only consider Small Signal model. Q & Q transistors - Frez- Smalbez They 5 @gm,ibe, us For relles, verres V x = -gm, ribe, rez Vbe, = V8 VX - - 9m, Vgren> Vahe -gm, re2

for SC finding finding vylux consider only og transistor Small Signal model @gm, uber Tech Vy=-gma vbez RC2 .. But Ubez=-vx Vy a- gm2 (ra) Rea Vy="9m2 VaR cz > 1 y = m Rcz] vy= g n2 RC2.x-gm, uska [ Vy = - gmp Rcq ( from er af Vs 9m2 = fica] Ma unam, eczny

Vous tinding by consider and on small signal model grabben rez rez bez @ gmyvben Frau {RES ubey & rey ovout I PEY Assume VA Node Apply voltage division An Hy Vout= VAXREY reut Rey VA 2 Yout [Reutreus REU. Apply nodal Analysis at VA: VA +VA-Vy rez VA-vout = 0 rey E3 Trey VA [ RE 3 + + 3 + + rey J -vout a za tu 703

. But va- vant ( Peu treyf yout REU I vout ( REG tre4y (1 + + + 7-vout= ut rez Reatrey 1 r regreut rey REstREjde, TIRES rezoey REY yout | rey-(Reutrey] [regrey freu RESTREX REG. RE38 E3 reiz RESTREzrez z a REU Rezret reu-[Reatrey] [regreut reyt REgt Restres]