OLLEGE OF ENGNEENG PUTAJAYA AMPUS FNAL EXAMNATON SPEAL SEMESTE 03 / 04 POGAMME SUBJET ODE SUBJET : Bachelor of Electrcal & Electroncs Engneerng (Honours) Bachelor of Electrcal Power Engneerng (Honours) : EEEB73 : ELETON ANALYSS AND DESGN DATE : Aprl 04 TME : 3 hours NSTUTONS TO ANDDATES:. Ths paper contans Sx (6) questons n Nne (9) pages.. Answer ALL questons. 3. Wrte all answers n the answer booklet proded. 4. Wrte answer to dfferent queston on a new page. 5. For all calculatons, assume that T = 6 m. THS QUESTON PAPE ONSSTS OF NNE (9) PNTED PAGES NLUDNG THS OE PAGE. Page of 9
Queston [0 marks] Desgn a dfferental amplfer usng NPN bpolar juncton transstors (BJT) based by a threetransstor current source, also usng NPN BJT. The three-transstor NPN BJT current source (conssts of Q, Q, Q 3, and ) s basng the dfferental amplfer (conssts of Q 4, Q 5, and resstors ) wth a ma constant current. The transstor parameters are: = 00, BE (on) = 0.7 and A =. The crcut parameters are: + = 5, - = -5. For the dfferental amplfer B4 = B5 = 0, and s gen as k. () Draw and label the crcut dagram of your desgn clearly. [5 marks] () Show clearly all calculatons and alues as accurate as possble wth regard to the desgn. You are requred, n partcular, to calculate the alues of the resstor n the current source, E, and E4. [5 marks] Page of 9
Queston [0 marks] The crcut n Fgure shows a par of PNP bpolar juncton transstors as nput deces and a par of NPN bpolar juncton transstors connected as an acte load. The basng current Q = 0. ma, and the transstor parameters are β = 00, and A = 00. () Determne O such that the dc currents n the dfferental amplfer are balanced. [3 marks] () alculate the open-crcut dfferental-mode oltage gan, A d. [4 marks] () Fnd the dfferental-mode oltage gan f a load resstance L = 50 k s connected to the output. [3 marks] + Fgure Page 3 of 9
Queston 3 [5 marks] (a) An dealzed class-b output stage, wth a complementary par transstors, as n Fgure has + = = 0, - = -0, and L = 00. Output sgnal oltage reads O = 6 sn t. The aerage power suppled by + and - to a class-b output stage s [ p /( L )]. Determne the followng: () The aerage current n the crcut. [ marks] () The aerage power delered to the load. [3 marks] () The aerage power dsspated n each transstor. [4 marks] () The power conerson effcency (η) of the output stage. [3 marks] Fgure (b) Descrbe the operaton of a class-b output stage as n Fgure 3. The cut-n oltage for both transstors s 0.7. How s ths output stage dfferent from the dealzed class-b output stage? [3 marks] Fgure 3 Page 4 of 9
Queston 4 [0 marks] onsder the Darlngton par and emtter follower porton of the crcut n Fgure 4. The parameters are 7 = Q = 0.5 ma, 8 = ma, 4 = 5 k, and 3 = 0. k. For all transstors, the current gan s 90. Q has Early oltage of 0, whle Early oltage for Q 7 s. When necessary, redraw crcut or label the crcut parameters and state your assumptons when fndng the alues of the followng; () The nput resstance ( ) of the Darlngton par. [8 marks] () The small sgnal oltage gan of the Darlngton par. [ marks] Fgure 4 Page 5 of 9
Queston 5 [5 marks] Study the bas crcut and nput stage of 74 operatonal amplfer (op-amp) shown n Fgure 5 carefully. Gen that + = + and - = -. Assume BE for npn = EB for pnp = 0.6 (EXEPT for BE0 ). Neglect dc base currents. () Determne the alue of resstor 5 f bas current for Q s 8 μa, and + = + and - = -. [0 marks] () Assumng dc currents n the nput stage are exactly balanced, therefore dc oltage at collector of Q 6 = dc oltage at collector of Q 5. alculate 6. [5 marks] Fgure 5 Page 6 of 9
Queston 6 [0 marks] (a) Wth a feedback resstor ( ) of 50 kω, desgn an amplfer usng op-amp n nonnertng confguraton wth a closed-loop gan whch can be ared between to 6 /. The closed-loop gan can be ared usng a potentometer ( ) and a fxed-alue resstor ( F ). Draw clearly your crcut desgn. [6 marks] (b) For an amplfer crcut usng op-amps shown n Fgure 6, use approprate deal op-amp characterstcs to show that O = + when = = F = 00 kω. [6 marks] Fgure 6 Page 7 of 9
Page 8 of 9 (c) For a generalzed summng op-amp as shown n Fgure 7 the total output oltage ( O ) s the sum of the nddual terms, or where Wth the smallest resstor alue allowable n the crcut s 5 kω, desgn a summng opamp smlar to Fgure 6b to produce the output of [8 marks] Fgure 7 -END OF QUESTON PAPE- B A P N B P A P N F F F O 4 3 4 3 5 0 5 O
Page 9 of 9 APPENDX BAS FOMULA BJT MOSFET Q A o T Q m Q T m B E E B S S r g r r g e e T EB T BE sgnal ;Small ;PNP ;NPN / / DQ o DQ m p ox p p TP SG p D TP SG SD n ox n n TN GS n D TN GS DS r g L W k L W L W k L W sgnal ;Small ] [ (sat) MOSFET ;P ] [ (sat) MOSFET N ;? ' '