Microelectronic Circuits

Transcription

1 Mcroelectronc Crcuts Slde 1

2 Introducton Suggested textbook: 1. Adel S. Sedra and Kenneth C. Smth, Mcroelectronc Crcuts Theory and Applcatons, Sxth edton Internatonal Verson, Oxford Unersty Press, Suggested Reference Books: 1. Rchard. C. Jaeger, Mcroelectronc Crcut Desgn, McGraw-Hll Companes Inc., Internatonal Edton, Muhammad Rashd, Introducton to PSpce Usng OrCAD for Crcuts and Electroncs 3 rd Edton, Pearson Educaton. Slde 2

3 Introducton Instructor-n-charge : Dr. Abdul Razak, Instructors : Dr. Abdul Razak, Slde 3

4 Introducton By the end of ths semester, you wll able to Know bascs of Mcroelectronc Crcuts ncludng Transstor Crcuts for mcro electroncs leel Study BJT and MOSFET amplfer characterstcs Multstage amplfers Feedback amplfes Output stage amplfes Power amplfers Dfferental Amplfers Frequency responses characterstcs of all the aboe Slde 4

5 Introducton Pre-requstes Bascs of BJT and MOSFET (Constructon and workng) Elementary crcut theory Concept of frequency response Bascs of acte and passe elements Bascs of oltage, current, power and ther relaton Slde 5

6 Introducton What s Mcroelectronc Crcuts? It s the ntegrated crcut (IC) technology capable of producng crcuts that contan mllons of components on a sngle chp. The area of such chp s of the order mm Examples: Dgtal computer Mcroprocessor Slde 6

7 Introducton Transstor Collector Base Emtter Slde 7

8 Introducton The frst transstors were created at Bell Telephone Laboratores n 1947 Wllam Shockley, John Bardeen, and Walter Brattan created the transstors n and effort to deelop a technology that would oercome the problems of tubes J. Bardeen,W. Brattan and W. Shockley, BJT C B E Slde 8

9 Introducton A transstor s a 3 termnal electronc dece made of semconductor materal. The word transstor s a combnaton of the terms transconductance and arable resstor Today an adanced mcroprocessor can hae as many as 1.7 bllon transstors. Slde 9

10 Introducton Before transstors were nented, crcuts used acuum tubes: Fragle, large n sze, heay, generate large quanttes of heat, requre a large amount of power. Frst ENIAC computer was proposed by John Mauchly Slde 10

11 Introducton NPN Transstor Hgh potental at collector Low potental at emtter Allows current flow when the base s gen a hgh potental Slde 11

12 Introducton PNP Transstor Hgh potental at emtter Low potental at collector Allows current flow when base s connected to a low potental Slde 12

13 Introducton Gordon Moore Co-founder of Intel Slde 13

14 Introducton to Amplfer What s an amplfer?? A system whch amplfy a small quantty nto large quantty In Electroncs engneerng the amplfcaton of Electrcal quanttes such as oltage, current and Power s consdered. BJT and MOSFETs can be used as an amplfer. These components are the basc buldng blocks of the amplfer. Amplfer crcuts are embedded n small package n many stages and aalable n mcro leel. Slde 14

15 Introducton to Amplfer Sgnal Amplfcaton Let us consder a Mcrophone ( Sound-Electrcal sgnal Transducer), A Output of the mcrophone s rased to mv. It s called as sgnal amplfcaton. The amplfer need to be lnear. Slde 15

16 Introducton to Amplfer Sgnal Amplfcaton Let output of the amplfer be 0 (t) for an nput of (t) at tme nstant t A The nput output relaton s 0 (t)=a (t) Where A s called as Gan of the amplfer. Slde 16

17 Introducton to Amplfer Amplfer Crcut Symbol Slde 17

18 Introducton to Amplfer Sgnal Amplfcaton Let output of the amplfer be 0 (t) for an nput of (t) at tme nstant t Slde 18

19 Introducton to Amplfer Voltage Gan A 0 t t Power Gan( A p ) Load Power Input Power ( P ) L ( P ) I 0 I 0 I Current Gan( A ) 0 I Slde 19

20 Introducton to Amplfer Gans n Decbels: Voltage gan n decbels =20 log A Current gan n decbels =20 log A I Power gan n decbels =10 log A p Slde 20

21 Introducton to Amplfer Basng of Amplfer: Amplfer need power supples to operate. Typcal amplfer requres two power supples as shown below Slde 21

22 Introducton to Amplfer Basng of Amplfer: The net dc power delered to the Load s P dc =V 1 I 1 +V 2 I 2 If the power dsspated n the amplfer s denoted by P dss The power balance equaton for the amplfer s P dc +P I = P L +P dss where P I = Power drawn from the sgnal P L = power delered to the Load PL Amplfer effcency 100 P dc Slde 22

23 Transfer Characterstcs & Basng Practcal amplfer may exhbt nonlnearty n ts transfer characterstcs. Slde 23

24 Transfer Characterstcs & Basng The operatng pont s selected by the basng of the transstor amplfer crcuts. Ths s done as shown below. where I I ( t) ( t) V I ( t) total nstantaneous nput where O O ( t) V O o ( t) ( t) total nstantaneous output o ( t) A ( t) A d d O I at Q Slde 24

25 Transfer Characterstcs & Basng A s slope of the almost lnear segment of the transfer cure. So for the lnear amplfcaton, there s a lmtaton: - the nput sgnal must be kept suffcently small so that nput ampltude wll not reach non-lnear porton Ths dstorton s undesrable Ths approxmaton s called as small-sgnal approxmaton Slde 25

26 Crcut Model for Amplfer 0 Where A o s the oltage gan of the unloaded amplfer (Open Crcut oltage) Slde 26

27 Crcut Model for Voltage Amplfer R s called as nput resstance accounts for the amount of current drawn from the sgnal source. Ro s called as output resstance accountng the current suppled to the Load. Specfc oltage amplfer model wth sgnal source s 0 Slde 27

28 Crcut Model for Voltage Amplfer 0 Applyng Voltage-Dder rule at output sde we get RL A o o R R L o Voltage Gan ( A ) o A o R L R L R o Slde 28

29 Crcut Model for Voltage Amplfer Voltage Gan ( A ) o A o R L R L R o In order not lose gan n couplng the amplfer output to a load, the R o must be smaller than the R L. Ideal amplfer wll hae Zero R o (output resstance) When R L = A =A o Slde 29

30 Crcut Model for Voltage Amplfer s R To make nput s =, nput resstance R >> R s R R s Ideal amplfer has R = The oerall oltage gan s gen by OerallVoltage Gan ( A ) o s A o R R R s R L R L R o Slde 30

31 Voltage Amplfer Open crcut oltage gan Ideal Characterstcs R = R o = 0 A o o o 0 ( V / V ) Slde 31

32 Current Amplfer Short crcut oltage gan A s o o 0 ( A/ A) Ideal Characterstcs R = 0 R o = Slde 32

33 Transconductance Amplfer Short crcut Transconductance A s o o 0 ( A/ V ) Ideal Characterstcs R = R o = Slde 33

34 Transrsstance Amplfer Open crcut Transconductance R Ideal Characterstcs R = 0 R o = 0 m o o 0 ( V / A) Slde 34

35 Example A Transstor amplfer has the transfer functon e 40 I Whch apples for I 0V and V. Fnd the lmt L and and the correspondng alue of I L. Also fnd the DC alue of based oltage VI that results n V0 = 5 V and the oltage gan at the correspondng operatng pont. Slde 35

36 Cascaded Amplfer Many applcatons cannot be handle wth sngle amplfers n order to meet the specfcaton of a gen amplfcaton gan, nput resstance and output resstance. To achee ths, the amplfer crcuts can be connected n seres commonly called as cascaded amplfers. Ths can be done ether to ncrease the oerall small-sgnal oltage gan or prode an oerall oltage gan greater than 1 wth a ery hgh nput resstance and low output resstance Slde 36

37 Cascaded Amplfer The frst stage s requred to hae a large nput resstance. Intermedate stage s requred to amplfy the gan Last stage s requred to hae a low output resstance. Slde 37

38 Example of Cascaded Amplfer Slde 38

39 Cascaded Amplfer Input to the frst stage s fracton of the source oltage, Applyng oltage dder, we get 1 1M V / V 1M 100k s Voltage gan of the frst stage s obtaned by consderng nput resstance of the second stage as Load resstance of the frst stage, we get 2 100k A V / V 1 100k 1k 1 Slde 39

40 Cascaded Amplfer Smlarly oltage gan of the second stage s obtaned by consderng nput resstance of the thrd stage as load resstance of the second stage, we get 3 10k A V / V 2 10k 1k 2 Fnally oltage gan of the output stage s gen by, L 100 A V / V Slde 40

41 Cascaded Amplfer The total gan of the three stages s now A A 1 A 2 A 3 818V / V Voltage gan from source to load s gen by L s A s 746V / V In db 57.4dB Slde 41

42 Cascaded Amplfer Current Gan L o A A A/ s 1M In decbels db A Power Gan A p P P L I L 1 o A A 818x 8.18x x 10 8 W / W In decbels 98.3 db Slde 42

43 Frequency Response Consder a lnear amplfer wth an sne-wae nput wth an ampltude V and frequency w. Amplfer output also a sne wae wth same frequency, and may hae dfferent ampltude and shfted n phase relate to the nput. Slde 43

44 Frequency Response Now rato of output ampltude Vo to the nput ampltude V at the test frequency s the magntude of the amplfer gan and angle Ø s the phase of the amplfer transmsson. Vo T ( w) and T ( w) V If we plot the aboe magntude and phase alue ersus frequency, we get ampltude response and phase response of the amplfer, respectely. Slde 44

45 Frequency Response Slde 45

46 Ealuatng frequency response of the Amplfer Amplfer equalent model wth reacte components such as nductors and capactors has to be used to ealuate the frequency response. L leads to sl and C leads to 1/sC where s = jw The nput/output relaton s wrtten n terms of transfer functon. V ( s) o T ( s) V ( s) Slde 46

47 Sngle Tme Constant crcut Consder RC crcut shown below Low Pass Crcut Hgh Pass Crcut The aboe crcut has tme constant τ = RC Slde 47

48 Frequency Response of STC Transfer Functon T(s) Low Pass Hgh pass Transfer Functon (for physcal frequency) Magntude Response Phase Response K 1 ( w/ w ) 2 0 K 1 ( w w 1 w 1 w0 tan ( ) tan ( ) w w 0 2 / ) 0 Slde 48

49 Frequency Response of Low Pass Crcut Slde 49

50 Frequency Response of Hgh Pass crcut Slde 50

51 Small sgnal model of BJT The heart of the small sgnal model s Transconductance amplfer. It can be represented by nput resstance between B and E, Short crcuted Transconductance and output resstance. Slde 51

52 Example: Small sgnal model of BJT Dere an Expresson for oltage gan magntude for the case 0 s and ealuates ts Rs 5 k, rπ 2.5k, gm 40mA/ V, r0 100k, and R L 5k What would be the gan alue be f the effect of ro were Neglected? Slde 52

53 Example: Small sgnal model of BJT Dere an Expresson for Rn Slde 53