β A Constant-G m Biasing

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1 p 2002 EE 532 Anal IC Des II Pae 73 Cnsan-G Bas ecall ha us a PTAT cuen efeence (see p f p. 66 he nes) bas a bpla anss pes cnsan anscnucance e epeaue (an als epenen f supply lae an pcess). Hw h we achee sla esuls CMO anal ccus? Us he bea ulple cuen efeence. As yu ay ecall, he bea ulple cuen efeence (Fue yu ex p yu nes), when pea sn es saua, eneaes an pu cuen escbe by I ef 2 2 β K 2 Then a MOFET (le s call ece M A ) base by hs cuen an pea sn es saua wul hae a anscnucance escbe by A 2β I A ef ubsu f I ef, A 2β A 2 2 β K 2 2 K β A β Ths esul s epenen f MOFET paaees (such as µ an V TH ) an supply lae. The aa A e epeaue, hwee, s ecly affece by he epeaue ceffcen f. An, f cuse, he abslue accuacy f ecly pacs he abslue accuacy f A.

2 p 2002 EE 532 Anal IC Des II Pae 74 Aplfes Thee ae 3 basc aplfe ccu ples: ) he e aplfe (cn-suce f 0Ω), 2) he cn-ae aplfe, an 3) he cn-a aplfe (leel-shfe/buffe). T bee unesan he sall-sal abues f each f hese cnfuas ne us be aely fala wh he espece sallsal els. e s sa by ee he sall-sal lae a a -ban f each aplfe ply. Ine Aplfe wh suce eenea. V DD s s b F he abe -ban sall-sal ccu el we bsee ha

3 p 2002 EE 532 Anal IC Des II Pae 75 an Apply KC a he a ne, s s b ubsu f s,, an us b, ( ) ( ) If >>, an >>, hen ( ) If we can als nelec by effec, hen a -ban. If s 0Ω (n suce eenea,.e., cn-suce) O, f >> (lea a)..

4 p 2002 EE 532 Anal IC Des II Pae 76 Cn-Gae Aplfe V DD V bas s s b F he ban sall-sal ccu el we bsee ha an s Apply KC a he a ne, s b ubsu f s,, an us b,

5 p 2002 EE 532 Anal IC Des II Pae 77 ( ) ( ) ( ) ( ) If s ey lae an >>, hen ( ) ( ) a -ban. If we can als nelec by effec, hen If s 0Ω (.e., en by an eal lae suce). O, f >> (lea a).

6 p 2002 EE 532 Anal IC Des II Pae 78 Cn-Da Aplfe (leel-shfe/buffe) he uce Fllwe V DD s s b F he ban sall-sal ccu el we bsee ha an s Apply KC a he suce ne, s b ubsu f s,, an us b, ( ) ( )

7 p 2002 EE 532 Anal IC Des II Pae 79 If s ey lae, hen ( ) ( ) a -ban. If we can als nelec by effec, hen whch appaches uny, f >>. Ne ha all hee f he hese aplfe cnfuas hae an effece anscnucance, G, escbe by G T suaze he -ban sall-sal lae a esuls f each f hee aplfe cnfuas: f he e aplfe wh suce eenea, G ; f he cn-ae aplfe, G ; an f he cn-a aplfe (leel-shfe/buffe), G.

8 p 2002 EE 532 Anal IC Des II Pae 80 M-ban all-al Ipeance Analyss V DD,ae,a V bas,suce k he ae,,ae. By lk he a,, a us he esuls f peus he cuen sk/suce scuss. Bu, lk he suce, cnse he -ban sall-sal el f he abe ccu. F splcy, by effec has been nelece. s s s, suce

9 p 2002 EE 532 Anal IC Des II Pae 8 Apply KC a he suce ne, s [Eqn. ] an a he a, s [Eqn. 2] ubsu eqn. eqn. 2: ( ) s suce, F lae, suce, an f >>, hen suce,.

10 p 2002 EE 532 Anal IC Des II Pae 82 Ace as Us an ace la,.e., MOFET(s), eplace a passe la ess can aacally euce he eque chp aea f he ccu whle als help puce uch hhe as (ue he penally hh sall-sal essance an ace la can pe). An ace la can be pleene us a ae-a cnnece (a.k.a. e-cnnece) MOFET a cuen suce/sk. Aplfes wh ae-a cnnece ace las en achee lae fequency banwhs bu lw a ue he elaely lw pu peance. ee Fue 22. f exaples f MO aplfes us aecnnece ace las. Aplfes wh cuen suce/sk ace las en achee hhe a ue he hh pu peance, bu a he expense f banwh. The casce aplfe s well sue f ache bh a an lae banwh. Back he ae-a cnnece ace la aplfe, le us cnse s fequency espnse e eal. ee he cn-suce aplfe Fue In hs scheac he ece capacances asscae wh M an M2 ae explcly shwn. Cnsequenly, he ccu has w C e cnsans ne a he pu an he he a he pu.

11 p 2002 EE 532 Anal IC Des II Pae 83 The pu C e cnsan s en by whee C τ ( C C C ) s MI s b ( ) A C MI C 2 Ne he fluence f Mlle capacance an suce essance,, n hs ccu s pu e cnsan, τ. A he pu, τ ( Cs2 CMO Cb Cb2 ) 2 whee 2 C MO C C. A Theefe he aplfe s fequency espnse s escbe by 2 A ( f ) f f j j f f whee f (/2πτ ) an f (/2πτ ).

Active Load. Reading S&S (5ed): Sec. 7.2 S&S (6ed): Sec. 8.2

Active Load. Reading S&S (5ed): Sec. 7.2 S&S (6ed): Sec. 8.2 cte La ean S&S (5e: Sec. 7. S&S (6e: Sec. 8. In nteate ccuts, t s ffcult t fabcate essts. Instea, aplfe cnfuatns typcally use acte las (.e. las ae w acte eces. Ths can be ne usn a cuent suce cnfuatn,.e.