Design of Analog Integrated Circuits

Transcription

1 Desgn f Analg Integrated Crcuts I. Amplfers Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 1

2 Oerew Basc MOS amplfer structures Cmmn-Surce Amplfer Surce Fllwer Cmmn-Gate Amplfer Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 2

3 Befre We Me On The whle curse s t desgn a real amplfer What are the real prpertes f a real amplfer? Hw t make nn-deal clse t deal? We wll cnsder Fnte gan s. nfnte Input mpedance Output mpedance Nnlnearty Later, een mre Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 3

4 Amplfer What s an amplfer? An essental crcut blck fr analg sgnal prcessng An amplfer generally s a nn-lnear crcut blck. ( t ) ( t) A1 ( t) 2 n A1 ( t ) A 2 ( t ) A n ( t ) What we generally want as an amplfer s a lnear amplfcatn. If the nput sgnal (t) s small enugh, we hae Here, A 1 s the amplfer small sgnal gan. All the hgh rder terms are neglgble due t small (t). Mst analg sgnal that needs amplfcatn can be categrzed as small sgnal and thus a generally nn-lnear amplfer can be lcally (arund the bas pnt) lnearzed t characterze ts perfrmance. ecall: MOSFET small-sgnal equalent crcut Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 4

5 Amplfer Crcut Symbl (a) Symbl fr a dfferental amplfer. (b) Symbl fr a sngle-ended amplfer. Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 5

6 Ideal Fnte-Gan Amplfer ltage gan and (sgnal) pwer gan A A p I 20lg A ( db) eal electrcal pwer s dfferent! Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 6

7 Gan=5 Amplfer 2 / 1 = 5 Assumptn fr Ideal Opamp Infnte gan What f the actual gan s nt nfnte? = 0.1 Opamp pen lp Gan A = 1000 =? x =? Opamp pen lp Gan A = 100 =? x =? Gal #1 fr pamp desgn -- Hgher pen lp gan wth lmted resurces (pwer, area) x A C L Nde shuld nt be gnred NOW Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 7

8 Cmmn Surce Amplfer As an Opamp Whch part f the cure has hgher gan? Operatng pnt, DC analyss, AC analyss, transent analyss Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 8

9 CS Amplfer Analyss: Lnear regn DC Analyss (Lnear egn) DD I d D DD C W n x [2( ) 2 ] 2 L D n t ut ut Equalent Crcut g m C n x W L ut n C n x W L 1 ( GS t ) ut DD n n D DD W 1 ncx D ( n t ) L Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 9

10 DC Analyss (Saturatn egn) 2 ) ( 2 t n D L W x C n DD D d I DD Small Sgnal Analyss ) ( 0 t n x n m m L W C g G D r 0 ) ( 0 D m r g a CS Amplfer Analyss: Saturatn egn Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 10

11 CS Amplfer: Maxmum ltage Gan lm D a g m r gm I D r 1/ I D lm a 1/ D I D Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang

12 CS Amplfer: Increasng ltage Gan lm D a g m r 2 C n x W L I D 1 I D 2 C n x W L 1 I D T ncrease A : Increase W/L Increase L () Decrease I D Trade ff: Larger dece sze, larger dece capactance Larger tme cnstant, lw speed Smaller current, lwer speed Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 12

13 CS Amplfer As the Opamp Put nt System Perspecte Questn: Hw far s ths crcut frm the gan=5 crcut whch s my desgn target? Hw can I mpre the stuatn? Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 13

14 Sme Mre Nn-Idealtes -- Input Impedance and Output Impedance s A s L L What s desred? L s much larger than s much larger than s

15 0 ) / ( A s A A A 0 ) / ( m A G ) / ( 0 0 ) / ( m A ltage Amplfer Current Amplfer Transcnductance Amplfer Transresstance Amplfer Fur Amplfer Types

16 ) ( ) ( t t I I ) ( ) ( t t O O ) ( ) ( t A t atq I O d d A Q shall be chsen n the mddle f the transfer cure Anther eal Thng Amplfer s Nt S Lnear

17 Anther eal Stuatn -- Amplfer Saturatn L A I L A Hw t deal wth the nnlneartes Harmncs, THD

18 CS Amplfer wth Current-Surce Lad esstr lad: Dffcult t fabrcate resstr wth tghtly-cntrlled alues. Dffcult t fabrcate resstr wth a reasnable physcal sze. Gan Lnger transstrs yeld a hgher ltage gan Gan ncreases as I D decreases Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang

19 CS Amplfer wth Surce Degeneratn Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang

20 Equalent Gm f CS Amp wth Surce Degeneratn In presence f bdy effect and channel-length mdulatn G m I ut / n S [1 g m ( g m r g ) mb S ] r 1 g m ( g g ) m mb S Ntes: Usng nde x t smplfy the deratn; a technque yu shall be famlar f nt yet Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang

21 OUT f CS Amp wth Surce Degeneratn Ntes: Usng test current r ltage t dere the mpedance s a ery mprtant technque. Keep practcng wth ths technque. Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang

22 Surce Fllwer Gd fr bufferng and mpedance transfrmatn Leel Shfter the utput DC s ne GS lwer than the nput DC Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 22

23 Surce Fllwer Large Sgnal Analyss Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 23

24 Surce Fllwer Small-Sgnal Analyss Surce fllwer exhbts a unty ltage gan and a mderate utput mpedance, but at the cst f tw drawbacks: nnlnearty due t bdy effect and ltage headrm lmtatn due t leel shft Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 24

25 Surce Fllwer As a Buffer T dre a lw mpedance lad Wthut the buffer, the gan s abut g m ( small bg ) Wth the buffer, the gan s abut g m bg Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 25

26 Hw Abut a PMOS Surce Fllwer? Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 26

27 Cmmn-Gate (CG) Amplfer Merts: Hgh Gan Nn-Inertng Lw nput resstance when the utput s termnated wth reasnable mpedance (<<r ) Hgh utput resstance Part f a Cascde structure Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 27

28 CG Amplfer Small-Sgnal Analyss Nn-nertng! Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 28

29 CG Amplfer Input Impedance Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 29

30 CG Amplfer Wth Input Surce Impedance S OUT s the same as that f a CS amplfer wth surce degeneratn Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 30

31 CG Amplfer Wth Input Surce Impedance S Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 31

32 Summary f Sngle Stage Amplfers Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 32

33 Summary f Sngle Stage Amplfers Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 33

34 Summary f Sngle Stage Amplfers Cmmn-Surce Amplfer Hgh nput mpedance and hgh utput mpedance Inertng amplfer It makes a gd ltage amplfer when termnated wth a hgh mpedance Cmmn-Gate Amplfer Lw nput mpedance and hgh utput mpedance Nn-nertng amplfer It s useful t achee maxmum ltage gan f a cmmn surce stage (cascde amplfer) Surce Fllwer Hgh nput mpedance and lw utput mpedance Nn-nertng amplfer It s useful t shft the DC peratng pnt f sgnal It s als useful as a ltage buffer Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 34

35 Imprtant Characterstcs f Amplfers Large sgnal ltage transfer characterstcs Large sgnal ltage swng lmtatn Small sgnal, frequency ndependent perfrmance Gan Input mpedance Output mpedance Small sgnal frequency respnse Other prpertes Nse Pwer dsspatn Desgn f Analg Integrated Crcuts Fall 2012, Dr. Guxng Wang 35