Part III Lectures Field-Effect Transistors (FETs) and Circuits

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1 Part III Lecture 5-8 Feld-Effect Trantr (FET) and Crcut

2 Unverty f Technlgy Feld-Effect Trantr (FET) Electrcal and Electrnc Engneerng epartment Lecture Ffteen - Page f 8 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn Feld-Effect Trantr (FET) Bac efntn: The FET a emcnductr devce whe peratn cnt f cntrllng the flw f current thrugh a emcnductr channel by applcatn f an electrc feld (vltage) There are tw categre f FET: the junctn feld-effect trantr (JFET) and the metal-xde-emcnductr feld-effect trantr (MOFET) The MOFET categry further brken-dwn nt: depletn and enhancement type A Cmparn between FET and BJT: FET a unplar devce It perate a a vltage-cntrlled devce wth ether electrn current n an n-channel FET r hle current n a p-channel FET BJT made a npn r a pnp a current-cntrlled devce n whch bth electrn current and hle current are nvlved The FET maller than a BJT and thu fr mre ppular n ntegrated crcut (IC) FET exhbt much hgher nput mpedance than BJT FET are mre temperature table than BJT BJT have large vltage gan than FET when perated a an amplfer The BJT ha a much hgher entvty t change n the appled gnal (fater repne) than a FET Junctn Feld-Effect Trantr (JFET): The bac cntructn f n-channel (p-channel) JFET hwn n Fg 5-a (b) Nte that the majr part f the tructure n-type (p-type) materal that frm the channel between the embedded layer f p-type (n-type) materal The tp f the n-type (p-type) channel cnnected thrugh an hmc cntact t a termnal referred t a the dran "", whle the lwer end f the ame materal cnnected thrugh an hmc cntact t a termnal referred t a the urce "" The tw p-type materal are cnnected tgether and t the gate "" termnal ran () ate () p n-channel p n p-channel n urce () (a) Fg 5- (b)

3 Unverty f Technlgy Feld-Effect Trantr (FET) Electrcal and Electrnc Engneerng epartment Lecture Ffteen - Page 2 f 8 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn Bac Operatn f JFET: Ba vltage are hwn, n Fg 5-2, appled t an n-channel JFET deve prvde a dran-t-urce vltage,, (dran ptve relatve t urce) and upple current frm dran t urce, I, (electrn mve frm urce t dran) et the revere-ba vltage between the gate and the urce,, (gate baed negatve relatve t the urce) Input mpedance at the gate very hgh, thu the gate current I 0 A evere bang f the gate-urce junctn prduce a depletn regn n the n-channel and thu ncreae t retance The channel wdth can be cntrlled by varyng the gate vltage, and thereby, I can al be cntrlled The depletn regn are wder tward the dran end f the channel becaue the revere-ba vltage between the gate and the dran grater than that between the gate and the urce epletn regn I I 0A p p n Electrn flw Fg 5-2 JFET Charactertc: When 0 and < P (pnch-ff vltage)*: I re lnearly wth (hmc regn, n-channel retance cntant), a hwn n Fg 5-3 When ncreaed t a level where t appear that the tw depletn regn wuld "tuch", a cndtn referred t a pnch-ff wll reult The level f that etablhe th cndtn referred t a the pnch-ff vltage and dented by P

Increang retance due t narrwng channel n-channel retance ( ) When 0 and P : I reman at t aturatn value I

value: The effect f the appled negatve-ba t etablh depletn regn mlar t the btaned wth 0 but at lwer level

4 Unverty f Technlgy Feld-Effect Trantr (FET) Electrcal and Electrnc Engneerng epartment Lecture Ffteen - Page 3 f 8 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn 0 _ p n p I < P _ Fg 5-3 I 0 I (ma) P Increang retance due t narrwng channel n-channel retance ( ) When 0 and P : I reman at t aturatn value I beynd P, a hwn n Fg _ p n p I P _ I 0 I (ma) P aturatn level 0 ( ) Fg 5-4 When < 0 and me ptve value: The effect f the appled negatve-ba t etablh depletn regn mlar t the btaned wth 0 but at lwer level f Therefre, the reult f applyng a negatve ba t the gate t reach the aturatn level at lwer level f, a hwn n Fg 5-5 Fg 5-5

2009-200 r Ahmed aadn Ezzulddn ummary: Fr n-channel JFET: The maxmum

vltage le than (mre negatve than) the pnch-ff level, the dran current 0 A

level, the current I wll range between I and 0 A, repectvely, a hwn n Fg

5 Unverty f Technlgy Feld-Effect Trantr (FET) Electrcal and Electrnc Engneerng epartment Lecture Ffteen - Page 4 f 8 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn ummary: Fr n-channel JFET: The maxmum current defned a I and ccur when 0 and P a hwn n Fg 5-6a 2 Fr gate-t-urce vltage le than (mre negatve than) the pnch-ff level, the dran current 0 A (I 0 A) a appearng n Fg 5-6b 3 Fr all level f between 0 and the pnch-ff level, the current I wll range between I and 0 A, repectvely, a hwn n Fg 5-6c (a) (b) (c) Fg 5-6 Fr p-channel JFET a mlar lt can be develped (ee Fg 5-7) Fg 5-7

6 Unverty f Technlgy Feld-Effect Trantr (FET) Electrcal and Electrnc Engneerng epartment Lecture Ffteen - Page 5 f 8 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn hckley' Equatn: Fr the BJT the utput current I C and nput cntrllng current I B were related by β, whch wa cndered cntant fr the analy t be perfrmed In equatn frm: I cntrl varable β C I B cntant In the abve equatn a lnear relatnhp ext between I C and I B Unfrtunately, th lnear relatnhp de nt ext between the utput (I ) and nput ( ) quantte f a JFET The relatnhp between I and defned by hckley' equatn: cntrl varable 2 I I [5] P cntant The quared term f the equatn wll reult n a nnlnear relatnhp between I and, prducng a curve that grw expnentally wth decreang magntude f Tranfer Charactertc: Tranfer charactertc are plt f I veru fr a fxed value f The tranfer curve can be btaned frm the utput charactertc a hwn n Fg 5-8, r t can be ketched t a atfactry level f accuracy (ee Fg 5-9) mply ung hckley' equatn wth the fur plt pnt defned n Table 5- Fg 5-8

7 Unverty f Technlgy Feld-Effect Trantr (FET) Electrcal and Electrnc Engneerng epartment Lecture Ffteen - Page 6 f 8 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn Table 5- I I P () I (ma) 0 I 03 P I / 2 05 P I / 4 P 0 2 I (ma) I I / 2 0 I P 05 P 03 P Fg 5-9 / 4 ( ) Imprtant elatnhp: A number f mprtant equatn and peratng charactertc have ntrduced n the lat few ectn that are f partcular mprtance fr the analy t fllw fr the dc and ac cnfguratn In an effrt t late and emphaze ther mprtance, they are repeated belw next t a crrepndng equatn fr the BJT The JFET equatn are defned fr the cnfguratn f Fg 5-0a, whle the BJT equatn relate t Fg 5-0b (a) Fg 5-0 (b) JFET BJT 2 I I P IC βi B I I IC I E I 0A BE 0 7

8 Unverty f Technlgy Feld-Effect Trantr (FET) Electrcal and Electrnc Engneerng epartment Lecture Ffteen - Page 7 f 8 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn Trancnductance Factr: The change n dran current that wll reult frm a change n gate-t-urce vltage can be determned ung the trancnductance factr g m n the fllwng manner: Δ I g Δ m The trancnductance factr, g m, (n pecfcatn heet, g m prvded a y f ) the lp f the charactertc at the pnt f peratn, a hwn n Fg 5- That, ΔI gm y f Δ cnt Fg 5- An equatn fr g m can be derved a fllw: g m 2 2 di d d I I d d Q pt P d P gm d 2 I 2I 0 P d P P P gm 2I P P [52] and 2I gm P [53] where g m the value f g m at 0 Equatn [52] then becme: gm gm P [54] JFET Output Impedance: The utput mpedance (r d ) defned n the dran (utput) charactertc f Fg 5-2 a the lpe f the hrzntal charactertc curve at the pnt f peratn In equatn frm: Δ rd [55] y ΔI cnt

9 Unverty f Technlgy Feld-Effect Trantr (FET) Electrcal and Electrnc Engneerng epartment Lecture Ffteen - Page 8 f 8 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn where y the utput admttance, wth the unt f μ, a appear n JFET pecfcatn heet JFET AC Equvalent Crcut: Fg 5-2 The cntrl f I d by g nclude a a current urce g m g cnnected frm dran t urce a hwn n Fg 5-3 The current urce ha t arrw pntng frm dran t urce t etablh a 80 phae hft between utput and nput vltage a wll a ccur n actual peratn The nput mpedance repreented by the pen crcut at the nput termnal and the utput mpedance by the retr r d frm dran t urce g I d d g _ g m g r d d Fg 5-3 Exerce: ketch the tranfer curve defned by I 2 ma and P 6 2 Fr a JFET wth I 8 ma and P 4, determne: a the maxmum value f g m (that, g m ), and b the value f g m at the fllwng dc ba pnt: 05, 5, and 25 3 ven y f 38 m and y 20 μ, ketch the JFET ac equvalent mdel

10 Unverty f Technlgy C Bang Crcut f JET Electrcal and Electrnc Engneerng epartment Lecture xteen - Page f 8 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn C Bang Crcut f JFET Fxed-Ba Cnfguratn: Fr the crcut f Fg 6-, I 0A, and I 0 Fr the nput crcut, 0, and Frm hckley' equatn: I I P 2 Fg 6- Fr the utput crcut, I and I 0, A graphcal analy hwn n Fg 6-2 Example 6-: Fg 6-2 Fr the crcut f Fg 6- wth the fllwng parameter: I 0 ma, P 8, 6, 2, MΩ, and 2 kω, determne the fllwng: Q, I Q,,,, and lutn: Frm Fg 6-3:, and I Q 5 6mA Q 2 I 6 (56m)(2k) Fg 6-3

11 Unverty f Technlgy C Bang Crcut f JET Electrcal and Electrnc Engneerng epartment Lecture xteen - Page 2 f 8 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn 2 elf-ba Cnfguratn: Fr the crcut f Fg 6-4, I 0A, and I 0 I I, and I Fr the nput crcut, 0, and I Fg 6-4 Frm hckley' equatn: I I P 2 elf-ba lne Fr the utput crcut, 0, ( and I ) A graphcal analy hwn n Fg 6-5 Example 6-2: Fg 6-5 Fr the crcut f Fg 6-4 wth the fllwng parameter: I 8 ma, P 6, 20, MΩ, kω, and 33 kω, determne the fllwng: Q, I Q,,,, and lutn: Chng I 4mA, we btan I ( 4m)(k ) 4 At the Q-pnt (ee Fg 6-6): Q 2 6, and I Q 2 6mA I ( ) 20 (26m)(k 33k) , and I ( 26m)(k ) 2 6 I 20 (26m)(33k) 42, Fg 6-6 r

12 Unverty f Technlgy C Bang Crcut f JET Electrcal and Electrnc Engneerng epartment Lecture xteen - Page 3 f 8 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn Example 6-3 (Cmmn-ate Cnfguratn): Fr the cmmn-gate cnfguratn f Fg 6-7, determne the fllwng: Q, I Q,,,, and C 2 C Fg 6-7 lutn: Chng I 6mA, we btan At the Q-pnt (ee Fg 6-8): I ( 6m)(680) 408 2, and I Q 3 8mA Q 6 I 2 (38m)(5k ) I ( 38m)(680) Fg 6-8

13 Unverty f Technlgy C Bang Crcut f JET Electrcal and Electrnc Engneerng epartment Lecture xteen - Page 4 f 8 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn Example 6-4 (egn): Fr the crcut f Fg 6-9, the level f Q and I Q are pecfed etermne the requred value f and lutn: Fg 6-9 Q kΩ I I 25m Q Q Plttng the tranfer curve a hwn n Fg 6-0 and drawng a hrzntal lne at I Q 25 ma wll reult n Q, and applyng I wll etablh the level f : Q ( ) 0 kω I 25m 4 Q Fg 6-0

14 Unverty f Technlgy C Bang Crcut f JET Electrcal and Electrnc Engneerng epartment Lecture xteen - Page 5 f 8 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn 3 ltage-vder Ba Cnfguratn: Fr the crcut f Fg 6-, I 0A I I, and 2 2 Fr the nput crcut, and I I 2 0,, I Fg 6- Frm hckley' equatn: I I P 2 ltage-dvder ba lne Fr the utput crcut, 0, ( and I ) A graphcal analy hwn n Fg 6-2 Example 6-5: Fg 6-2 Fr the crcut f Fg 6- wth the fllwng parameter: I 8 ma, P 4, 6, 2 MΩ, kω, 24 kω, and 5 kω, determne the fllwng: Q, I Q,,,, and lutn: 2 (6)(270k) M 270k I 82 I (5k ), when I 0mA : 82, and when 0 : I 82 ma 5k 2 At the Q-pnt (ee Fg 6-3): Q 8, and I Q 2 4mA Fg 6-3

15 Unverty f Technlgy C Bang Crcut f JET Electrcal and Electrnc Engneerng epartment Lecture xteen - Page 6 f 8 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn I 6 (24m)(24k) 0 24 I ( 24m)(5k ) 3 6 I ( ) 6 (24m)(24k 5k) 6 r , Example 6-6 (Tw upple): etermne the fllwng fr the crcut f Fg 6-4; Q, I Q,,, and lutn: Fg 6-4 Fr the nput crcut f Fg 6-4, I 0 (KL) and I 0A I I, I 0 I (5k ), fr I 0mA ; 0, and fr 0 ; I 0 6 ma 5k 67 At the Q-pnt (ee Fg 6-5): Q 0 35, and I Q 6 9mA Fr the utput crcut f Fg 6-4, I I 0, I ( ) Fg (69m)(8k 5k) 7 23 I 20 (69m)(8k )

16 Unverty f Technlgy C Bang Crcut f JET Electrcal and Electrnc Engneerng epartment Lecture xteen - Page 7 f 8 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn Example 6-7 (p-channel JFET): etermne Q, I Q, and fr the p-channel JFET f Fg 6-6 lutn: Fg ( 20)(20k) k 68k I 455 I (8k), when I 0mA : 4 55, and when 0 : I ( 455) 2 ma 8k 53 At the Q-pnt (ee Fg 6-7): Q 4, and I Q 3 4mA I ( ) 20 (34m)(27k 8) 4 7 Fg 6-7

17 Unverty f Technlgy C Bang Crcut f JET Electrcal and Electrnc Engneerng epartment Lecture xteen - Page 8 f 8 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn Exerce: Fr the cmmn-dran (urce-fllwer) cnfguratn f Fg 6-8, determne the fllwng: Q, I Q,,,,, and C 9 I 6mA P 4 C 2 MΩ 22kΩ Fg Fr the vltage-dvder ba cnfguratn f Fg 6-9, f 2 and 2, determne the value f Fg 6-9

18 Unverty f Technlgy JFET mall-gnal Analy Electrcal and Electrnc Engneerng epartment Lecture eventeen - Page f 7 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn JFET mall-gnal Analy Cmmn-urce Cnfguratn: The cmmn-urce cnfguratn crcut f Fg 7- nclude a urce retr ( ) that may r may nt be bypaed by a urce capactr (C ) n the ac dman g I C Z C C Z I C L Z Fg 7- Bypaed (abence f ): Fr the ac equvalent crcut f Fg 7-2, g I g d I Z g g m g rd Z Z L Fg 7-2 Input mpedance: Z Output mpedance: Apprxmate (neglectng r d ); Exact (ncludng r d ); Z (fr r 0 ) Z r d d L Z L Z L rd Z

19 Unverty f Technlgy JFET mall-gnal Analy Electrcal and Electrnc Engneerng epartment Lecture eventeen - Page 2 f 7 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn ltage gan: Apprxmate (neglectng r d ); Exact (ncludng r d ); g ( ), A g r ) g m, g L Av gm ( L ) A Z v Av Z Current gan: I A A I v Z L g v m ( L d Phae relatnhp: The negatve gn n the reultng equatn fr A v reveal that a 80 phae hft ccur between the nput and utput gnal Unbypaed (nclude f ): Fr the apprxmate ac equvalent crcut ( r Ω ) f Fg 7-3, d I g d I g Z g g m g r d Z L Fg 7-3 Output mpedance: Fr 0, I I g, wth that m g g ( I I ) 0 I I g m ( I I ), r I ( g m ) I ( g m ) and I nce I I, Then I ) I Z I, (, and,

20 Unverty f Technlgy JFET mall-gnal Analy Electrcal and Electrnc Engneerng epartment Lecture eventeen - Page 3 f 7 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn ltage gan: g ( ) m g L g g gmg > ( g m ) g A v gm ( L g m ) Cmmn-ran (urce-fllwer) Cnfguratn: The cmmn-dran (urce-fllwer) cnfguratn crcut hwn n Fg 7-4 I C g Z Z C C I L Fr the ac equvalent crcut f Fg 7-5, Fg 7-4 I g d g Z g g m g Z r d I L Fg 7-5 Input mpedance: Z [hgh] Output mpedance: Fr 0, I gmg I r I rd d > I, wth > I ( r g ), ( rd ) gmg g 0 d m

21 Unverty f Technlgy JFET mall-gnal Analy Electrcal and Electrnc Engneerng epartment Lecture eventeen - Page 4 f 7 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn and Z I [ r ( g )] d > Z r / g [lw] Z m d / gm (fr d gm ltage gan: g r ), A A g v v m g ( L d m r 0 ) g gmg ( L rd ) > [ gm ( L rd )] g, gm ( L rd ) [le than ] g ( r ) m L d gm ( L ) (fr rd 0 ) g ( ) Phae elatnhp: and are n-phae m L Cmmn-ate Cnfguratn: The cmmn-gate cnfguratn crcut hwn n Fg 7-6 I C C C I g Z Z L Fg 7-6 Fr the apprxmate ac equvalent crcut ( r Ω ) f Fg 7-7, d r d g I g m g d I Z g g Z L Fg 7-7

22 Unverty f Technlgy JFET mall-gnal Analy Electrcal and Electrnc Engneerng epartment Lecture eventeen - Page 5 f 7 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn Input mpedance: Z g / m [lw] (erve) gm Output mpedance: Z ltage gan: gmg ( L ), and g > A v gm ( L ) Phae elatnhp: and are n-phae Example 7- (Analy): Fr the JFET amplfer crcut f Fg 7-8 wth parameter g m 22 m, determne: Z, Z, Z, A v /, A I /I, Av / and Aume rd > 0 6 C I 2MΩ 24kΩ Z C C 20μF I L Z 47kΩ g 0μF kω 200m Z 2 270kΩ 2 03kΩ 2kΩ 20μF C Fg 7-8 lutn: Z 2M 027M 239kΩ Z A 2 4kΩ, Z L 2 4 7k 24k 59kΩ gm ( L ) (22m)(59k) 2 g (22m)(03k) v m

23 Unverty f Technlgy JFET mall-gnal Analy Electrcal and Electrnc Engneerng epartment Lecture eventeen - Page 6 f 7 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn Z ( 2)(239k) A Av 07 L 47k Z k Av ( 2)(239 ) Av 2 Z 239k k 0 A v g 2 0(200m) 420m A v Example 7-2 (egn): Cmplete the degn f the JFET amplfer crcut hwn n Fg 7-9 t have a vltage gan magntude f 75 db, ung a relatvely hgh level f g m fr th devce defned at Q P /4 Aume r > 0 d 20 C C g C 0μF kω 00m 0MΩ 0μF I 0mA P 4 C L 40μF 6kΩ Fg 7-9 lutn: Q P / 4 4/ 4, 2I 2(0m) gm 3 75m P, P 4 4 db) 20lg A 75 20lg A A 75, I ( 0 v 0 v v v gm L ) m(6k ) Q Q I 0m 5 625mA P 4 Q I Q 5625m( ) 78Ω A ( kω,

24 Unverty f Technlgy JFET mall-gnal Analy Electrcal and Electrnc Engneerng epartment Lecture eventeen - Page 7 f 7 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn Exerce: Fr each ne f the crcut hwn n Fg 7-0, determne: (a), and g m (b) Z, and Z (c) Av /, and A I / I 8 g I C 82μF 05kΩ Z 2MΩ 2 I 6mA P 6 Z C C I 82μF 33kΩ 22kΩ L g I C 56μF kω Z I 5mA P 4 33kΩ C C 56μF Z 2kΩ I L 47kΩ (a) Fg 7-0 (b) 2 Che the value f,, and L fr the JFET amplfer crcut f Fg 7- that wll reult n a gan f 8062 db Aume that I 8 ma, P 4, r d Ω, Q / 0375, and I Q /I 025 Calculate A /, and ketch v 6 C C C μf L g 0μF kω 3 50n (2π 0 )t m Fg 7-

25 Unverty f Technlgy Frequency epne f JFET Amplfer Electrcal and Electrnc Engneerng epartment Lecture Eghteen - Page f 5 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn Frequency epne f JFET Amplfer Lw-Frequency epne f JFET Amplfer: The Capactr C, C C, and C wll determne the lwer-cutff frequency (f L ) f the cmmn-urce JFET amplfer hwn n Fg 8-, but the reult can be appled t any JFET amplfer Fr the cutff-frequency f C, X > g C C C f L 2 π ( g ) where C Fr the cutff-frequency f C C, X > L C C g C C L Fg 8- π C f L C 2 ( L ) C eq where Fr the cutff-frequency f C, > eq X C C f L 2πeq where / g eq m The lwer-cutff frequency, f Max[ f L L, f L C, f L ]

26 Unverty f Technlgy Frequency epne f JFET Amplfer Electrcal and Electrnc Engneerng epartment Lecture Eghteen - Page 2 f 5 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn Hgh-Frequency epne f JFET Amplfer: The analy f the hgh-frequency repne f the JFET amplfer mlar t that encuntered fr the BJT amplfer A hwn n Fg 8-2, there are nterelectrde and wrng capactance that wll determne the hgh-frequency charactertc f the amplfer The capactr C g and C gd typcally vary frm t 0 pf, whle the capactance C d uually qute a bt maller, rangng frm 0 t pf C gd C C C C d g C W L C g C W C Fg 8-2 nce the crcut f Fg 8-2 an nvertng amplfer, a Mller effect capactance wll appear n the hgh-frequency ac equvalent crcut appearng n Fg 8-3 The cutff frequence defned by the nput and utput crcut can be btaned by frt fndng the Thevenn equvalent crcut fr each ectn a hwn n Fg 8-3 g Th C g g m g L Th C C C C C C CW C g CM W d M Th Th E Th C E Th C Fg 8-3

27 Unverty f Technlgy Frequency epne f JFET Amplfer Electrcal and Electrnc Engneerng epartment Lecture Eghteen - Page 3 f 5 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn Fr the nput crcut, f H 2π Th C and wth C Th W g C C C C C ( A ) C g M W g v gd Fr the utput crcut, f H 2π Th C and wth C Th W L C C C C C ( / A ) C d M W d v gd The hgher-cutff frequency, f Mn[ f H, f H H ] Example 8-: Fr the JFET amplfer crcut hwn n Fg 8-4, wth the fllwng parameter: I 8 ma, P 4, r d > 0, C gd 2 pf, C g 4 pf, C d 05 pf, C W 5 pf, and C W 6 pf a etermne f L, f H, and BW b ketch the frequency repne 20 47kΩ C C g C 00μF 0kΩ MΩ kω 05μF C L 2μF 22kΩ Fg 8-4

28 Unverty f Technlgy Frequency epne f JFET Amplfer Electrcal and Electrnc Engneerng epartment Lecture Eghteen - Page 4 f 5 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn lutn: Frm dc analy (ee Fg 8-5): Q 2, and I Q 2mA, g 2I Q 2(8m) 2 m P, P 4 4 m 2 Av g m ( L ) 2m(22k 47k) 3 elf-ba lne (k ) I Q-pnt ( P ) f L Hz 2π ( g ) C 2π (0k M )(00μ) 6, Fg 8-5 f L Hz C 2π ( L ) CC 2π (22k 47k)(05μ) 46, eq / gm k 05k 333 3Ω, f L Hz 2 eqc 239, π 2π (3333)(2μ) The lwer-cutff frequency, f L Max[ f L, f, ] L f C L Max[ 6,46,239] 239Hz I (ma) ( I ) I Q 2mA ( ) Q 2 C f C f 0 k M 9 kω, Th g 9 H C W C 2π Th g C ( A ) C 5 p 4 p ( 3)(2 p) 7 pf, v gd 94566kHz, 2π (99k)(7 p) 2 2k 47k kω, Th L 5 H C W C 2π Th d C ( / A ) C 6 p 05p ( /3)(2 p) 97 pf, v gd 57MHz, 2π (5k )(97 p) The hgher-cutff frequency, f Mn[ f, f ] H H H Mn[ 94566k,57M ] kHz The bandwdth, BW f H f L 94566k kHz

29 Unverty f Technlgy Frequency epne f JFET Amplfer Electrcal and Electrnc Engneerng epartment Lecture Eghteen - Page 5 f 5 ecnd Year, Electrnc I, r Ahmed aadn Ezzulddn The frequency repne fr the lw- and hgh-frequency regn and bandwdth are hwn n Fg 8-6 Av Av md db f LC f L - 3 db f L 0 00 k 0k 00k M 0M f L BW f H f H 00M f H f (lg cale) - 5 Fg 8-6 Exerce: Fr the JFET amplfer crcut f Fg 8-7, determne the lwer- and hgher-cutff frequence and ketch the frequency repne CW 3 CW 5 pf pf 20 g C dg 4 pf C g 6 pf C d pf C μf 5kΩ 2 220kΩ 68kΩ 39kΩ C C 68μF I 0mA P 6 C L 22kΩ 0μF 56kΩ Fg 8-7

, where. This is a highpass filter. The frequency response is the same as that for P.P.14.1 RC. Thus, the sketches of H and φ are shown below.

, where. This is a highpass filter. The frequency response is the same as that for P.P.14.1 RC. Thus, the sketches of H and φ are shown below. hapter 4, Slutn. H ( H(, where H π H ( φ H ( tan - ( Th a hghpa lter. The requency repne the ame a that r P.P.4. except that. Thu, the ketche H and φ are hwn belw. H.77 / φ 9 45 / hapter 4, Slutn. H(,