MOS Feld-Effec Trassrs (MOSFETs ecure # 4 MOSFET as a Amplfer k ( S Square law express s lear bewee ad. Need perae apprprae reg fr lear behaur. Cpyrgh 004 by Oxfrd Uersy Press, c.
MOSFET as a Amplfer S S Cpyrgh 004 by Oxfrd Uersy Press, c. 3 Graphcal era f Trasfer Characerscs S S Cpyrgh 004 by Oxfrd Uersy Press, c. 4
MOSFET as Swch ff c Cpyrgh 004 by Oxfrd Uersy Press, c. 5 Selec f Q P A d d Q s ery mpra e ha he selec f Q p shuld be made such a way ha he sgal s dsred/clpped, we ca see ha f he Q p s ear he upu wll be clpped ff ad f s clse rde budary sgal wll be dsred. S bascally, he Q p shuld be lwer ha ad hgher ha SQ hae maxmum swg. Hweer, e shuld e ha selec f Q p s depede wha yu selec he lad ressr, whch deermes he rasfer characerscs. Cpyrgh 004 by Oxfrd Uersy Press, c. 6 3
Aalyss: MOSFET as a ear Amplfer Cuff Segme X - A, Saura Segme A - Q - B cx ( ad frm hese w equas we ge O cx ( d we ca deerme ga A cx ( Q d Q Q ( A OQ OQ TrdeSegme B - C Q where ( usg he abe w equa ad subsug cx O O ( ad frm hese w equas we ge O cx ( eferece 4.43 Equa we kw rs cx ( OQ rs O Usually rs rs rs rs O Cpyrgh 004 by Oxfrd Uersy Press, c. 7 Example 4.8 P X : 0 0 O P A : 0 O P B : As we are he saura reg s O cx ( wesubsude abeas O s 0 cx ( 9 0 0 has w rs ad pssble es B B Therefre P C : O cx ( 0 8 (0 0.06 eferece 4.43Equa Nex s he basg he amplfer,sce he segme exeds frml 0 l may be weselec heq p a 4. s he curre OQ 0 4 0.333 ma 8 we ca calculaeer dre lage k 0.333 0.86 S we perae MOSFET a a dc gae surce lage lagega frm 4.40 A 8(.86 4.7 / Q.86 Cpyrgh 004 by Oxfrd Uersy Press, c. 8 4
Example 4.8 Supermpse he fllwg sgal a.86 (Q p Cx ( S a.74, (.74 0.75mA A.86, (.86 0.333mA A.89, (.89 0.397mA k a he +e & -e creme he dra curre, are hey same? Cpyrgh 004 by Oxfrd Uersy Press, c. 9 Example 4.8 The upu wll ary arud bas alue f OQ =4 A.74, 0.75mA ad 0 0.758 5. 05 A.89, 0.397mAad 0 0.3978.85 k a he upu fr +e ad e excurss? Cpyrgh 004 by Oxfrd Uersy Press, c. 0 5
Exercse 4.7 & 4.8 A Cpyrgh 004 by Oxfrd Uersy Press, c. O K ( { Q, O OQ, } Q Basg MOS Amplfer Crcus N a gd dea fr basg MOSFET? C x ( The use f fxed bas (csa ca resul a large arably he alue f. eces ad represe exremes amg us f he same ype. Cpyrgh 004 by Oxfrd Uersy Press, c. 6
Basg wh fxed gae lage G & hag a surce ressr S G S (a Basc Arrageme (b educed arably Cpyrgh 004 by Oxfrd Uersy Press, c. 3 Basg wh fxed gae lage G & hag a surce ressr S G S (c Praccal mplemea usg a sgle supply; (d Cuplg f a sgal surce he gae usg a capacr C C ; (e Praccal mplemea usg w supples. Cpyrgh 004 by Oxfrd Uersy Press, c. 4 7
Example 4.9 S S K G S As a rule f humb fr classcal basg we selec ad S such a way ha he lage s dded equally acrss, MOSFET (ra Surce & S, whch meas e hrd acrss hese hree cmpes. Cpyrgh 004 by Oxfrd Uersy Press, c. 5 Exercse 4.9 & 4.0 Frs fd ad he er lage,hefd S, ce yu hae S fd S. Nw calculae ew by subsug =- S = SS S Cpyrgh 004 by Oxfrd Uersy Press, c. 6 8
9 Basg: ra Basg: ra- -Gae Feedback essr Gae Feedback essr S Cpyrgh 004 by Oxfrd Uersy Press, c. 7 Basg Usg a Csa Curre Surce Basg Usg a Csa Curre Surce ( ( C C x SS EF x Cpyrgh 004 by Oxfrd Uersy Press, c. 8 EF
Exercse 4. & 4. Frs fd ad he, fr hs cfgura = S,fd. Nw calculae ew by subsug = = Cpyrgh 004 by Oxfrd Uersy Press, c. 9 0