College of Engineering Department of Electronics and Communication Engineering. Test 1 With Model Answer

Transcription

1 Name: Student D Number: Secton Number: 01/0/03/04 A/B Lecturer: Dr Jamaludn/ Dr Jehana Ermy/ Dr Azn Wat Table Number: College of Engneerng Department of Electroncs and Communcaton Engneerng Test 1 Wth Model Answer SEMESTER, ACADEMC YEAR 016/017 Subject Code : EEEB73 Course Ttle : Electroncs Analyss & Desgn Date : 19 Noember 016 Tme Allowed : hours nstructons to the canddates: 1. Wrte your Name and Student D Number. ndcate your Secton Number and Lecturer s Name. Wrte also your Table Number.. Wrte all your answers usng pen. DO NOT USE PENCL except for the dagram. 3. ANSWER ALL QUESTONS. Show clearly all your calculatons. Eery alue must be wrtten wth ts correct Unt. 4. WRTE YOUR ANSWER ON THS QUESTON PAPER. NOTE: DO NOT OPEN THE QUESTON PAPER UNTL NSTRUCTED TO DO SO. GOOD LUCK! Queston Number Q1 Q Q3 Total Marks Page 1

2 QUESTON 1 [40 marks] (a) Consder the three-transstor BJT current source as n Fgure 1(a). All transstors hae BE (on) = 0.6 and A = 10. Transstors Q 1 and Q are dentcal wth β = 80, whle Q 3 has β 3 = 50. Gen + = 10, - = -10, and O = 0.70 ma. () Calculate all transstor currents n the crcut, REF, and R 1. [1 marks] () What s the mnmum oltage at C? () How much reference current dffers from the bas current? () Descrbe any smlarty and dfference of ths current source wth the Wlson current source. [4 marks] Answers for Queston 1(a) Fgure 1(a) Page

3 Answers for Queston 1(a) (Contnued) Answers for Queston 1(a) () Calculate all transstor currents n the crcut, REF, and R 1. [1 marks] B1 = B [1] O = β B B = O / β = 0.7m/80 = 8.75uA [1.5] C1 = β B C1 = O = 0.7mA [1] E3 = B = (8.75u) =17.5uA [1] B3 = E3 / (1 + β 3 ) = 17.5u/51 =0.3431uA [1.5] REF = C1 + B3 =0.7m u = uA [] R 1 = ( + - BE (on) - ) / REF [] = (0 - (0.6)) / ( m) [] = 6.84 kω () What s the mnmum oltage at C? C = - + CE(mn) = = -9.4 [] () How much reference current dffers from the bas current? REF s 0.049% hgher than O OR dffers uA [] () Descrbe any smlarty and dfference of ths current source wth the Wlson current source. [4 marks] 1) ery close approxmaton of O to REF [] ) Lower output resstance by a factor of ( / ). [] Page 3

4 (b) Study a mult-transstor BJT current mrror shown n Fgure 1(b) thoroughly and carefully. Wth crcut analyss, load current for a mrror transstor Q N can be found usng ON REF (1 N) 1 where N s the total number of equalent mrror transstors nsde Q 1 to Q N n the crcut. Eery equalent mrror transstor s matchng wth the reference transstor Q R. Fgure 1(b) All transstors hae BE (on) = 0.7, β = 40, and A = 150. Gen + = 10, - = -10, and R 1 = 10 kω. () What s the total number of equalent mrror transstors (N) n the crcut? [4 marks] () Calculate REF, O1, O, O3, and ON n the crcut. [1 marks] () Fnd output resstance of the current mrror at transstor Q 3 (.e. R O3 ). [4 marks] Answers for Queston 1(b) Page 4

5 Answers for Queston 1(b) (Contnued) Answers for Queston 1(b) () What s the total number of equalent mrror transstors (N) n the crcut? [4 marks] N = 1 (for Q1) + 3 (for Q) + (for Q3) + 1 (for QN) = 7 [4] () Calculate REF, O1, O, O3, and ON n the crcut. [1 marks] REF = ( + - BE (on) - - ) / R 1 [] = ( (-10)) / (10k) = 1.93 ma [] ON = REF / (1 + (1 + N) / β) = (1.93 ma) / (1 + (1 + 7) / 40) = ma [] *Note O1 = ON = ma [] *Note O = 3 ON = 3x1.608 ma = 4.84 ma [] *Note O3 = ON = x1.608 ma = 3.16 ma [] *Note *Note: f answer for 1(b)() s not N = 7, may ge [1.5 marks] for alues of O1, O, O3, and ON based alue of N gen n 1(b)() on condton that respecte formula s correct. () Fnd output resstance of the current mrror at transstor Q 3 (.e. R O3 ). R O3 = A / O3 [] = 150 / 3.16m = kω [] [4 marks] Page 5

6 QUESTON [30 marks] Fgure shows a MOSFET cascode current source wth all transstors are regarded as dentcal. The transstor parameters are: TN = 0.5, K n = 80 A/, and = The crcut parameters are: + = +7, = 7, and REF = 10 A. (a) Calculate the GS of each transstor and O. [10 marks] (b) f REF symbol n the Fgure s replaced by another MOSFET transstor M 5 (but M 5 s NOT dentcal to M 1 to M 4 ) to act lke a resstor, what s the alue of GS5? [4 marks] (c) Determne the percent change n O as D4 changes from -3 to +3. [16 marks] Answers for Queston Fgure Page 6

7 Answers for Queston (Contnued) (a) Usng the formula of D = K n ( GS TN ) REF = K n ( GS1 TN ) 10 = 80 ( GS1 0.5) GS1 = GS = GS3 = GS4 = GS1 = O = D4 = D = K n ( GS TN ) = 10 A (b) + - GS5 - GS3 - GS1 = - GS5 = + - GS3 - GS1 - - = () (-7) = (c) R O = r O4 + r O (1+g m r 04 ) OR R O g m r 04 r O [Because approxmaton was also taught n the lecture] g m = K n O = (0.08m)(0.1m) = ma r O = r O4 = 1 O = 1 (0.0)(0.1m) = kω OR R O = k k[1+( m)( k)] = MΩ R O = ( m)( k)( k) = 34.0 MΩ OR O = D4 R O O = D4 R O = 3 ( 3) = μa M = 3 ( 3) = μa 34.0M [, marks] OR O 100% = % = % [, marks] O % = % = % O 10 O Page 7

8 QUESTON 3 [30 marks] Fgure 3 shows a crcut dagram for a BJT dfferental amplfer based wth a current source to prode bas current Q. Study the crcut dagram carefully. Transstor parameters are BE (on) = 0.7, β =, and A =. For the crcut dagram also, oltages measured at C1 and C are 4.5 respectely. (a) Calculate the alues for cm and d. [6 marks] (b) Determne the alue of Q. [6 marks] (c) Fnd the alue for CE. [6 marks] (d) Determne the dfferental-mode oltage gan (A d ) of the dfferental amplfer for a onesded output taken at C. [6 marks] (e) Draw and label clearly the full crcut dagram f the dfferental amplfer s based wth a Wdlar current source. [6 marks] Show clearly all your calculatons. Eery parameter must be wrtten wth ts correct Unt. Answers for Queston 3 (a) From Fgure 3: B1 = B = 0 [] cm = ( B1 + B ) / = 0 [] d = B1 - B = 0 [] (b) Gen: C1 = C = C1 R C = C1 = 4.5 [] C1 = 0.55 ma = C [] Q = C1 + C = 1.1 ma [] (c) Gen: C = 4.5 CE = C - E [] E = B - BE (on) = = -0.7 [, 1] CE = C - E = 4.5 (-0.7) = 5. [1] (d) A d = (g m R C )/ [] g m = C / T [] = 0.55m/6m = ma/ [1] A d = (g m R C )/ = (1.153m x 10k)/ = [1] Fgure 3 Page 8

9 Answers for Queston 3 (Contnued) (e) Dff amp: marks = 0.5 marks Total: 4 marks Page 9

10 Page 10 BASC FORMULA FOR TRANSSTOR BJT MOSFET 6 m sgnal ;Small 1 ;pnp ;npn / / T CQ A o CQ T T CQ m m C B E B E C S C S C r r g r g e e T EB T BE DQ o DQ m p p TP SG p D TP SG SD n n TN GS n D TN GS DS r K g L W k K K L W k K K 1 sgnal ;Small ] [ (sat) MOSFET ;P ] [ (sat) MOSFET N ;? ' ' A AC B B x C Bx Ax 4 0 Quadratc formula :