Ch. 9 Common Emitter Amplifier

Transcription

1 Ch. 9 Common mttr mplfr

2 Common mttr mplfr nput and put oltags ar 180 o -of-phas, whl th nput and put currnts ar n-phas wth th nput oltag. Output oltag ( V ) V V V C CC C C C C and V C ar -of-phas 10 μ 1 m 5 μ 0.5 m

3 C mttr sstanc Dynamc rsstanc of th bas-mttr pn juncton, ~ dpndng on V (or ) r ~ usful for th calculaton of oltag gan and nput mpdanc V 5mV From pn-juncton's dod quaton, xp[ V / k T ] 1 S d xp V / k T dv k T k T S S 1 dv d kt 1 kt r d dv S t room tmpratur ( T 300 K), k T 5 mv ( k oltzman's constant) r 5 mv Hgh r Low r

4 xampl 9.1 Dtrmn th ac mttr rsstanc for th transstor blow. Not: V VCC 1 5 mv V V V V r V 0.7(V)

5 C ta DC bta : currnt gan for dc (or constant) and C C dc C bta : currnt gan for th araton of ac (oscllatng) and C h F C a c h f Nonlnar charactrstc cur C put C nput

6 Capactors n mplfr () Couplng capactor for cascadd amplfr : C sgnal s connctd, whl DC sgnal s blockd ~ mult-stag amplfr Capact ractanc: X X C C 1 1 for DC sgnal ( 0) fc C 1 for hgh frquncy C sgnal ( 1) capact couplng V 4 V CC 3 4 drct couplng Q C1 3 4 V VCC Q 4

7 Capactors n mplfr () ypass capactor : C sgnal s groundd (short-crcut), whl DC sgnal s not affctd Short to ncras oltag gan!

8 Common-mttr mplfr Sgnals for a Two-Stag mplfr

9 C qualnt Crcut for Common mttr mplfr For th C charactrstcs analyss, 1. plac all dc sourcs wth a ground symbol ~ battry has an xtrmly low C ractanc.

10 C qualnt Crcut for Common mttr mplfr For th C charactrstcs analyss,. Mak a short crcut wth all capactors

11 mplfr Gan of Common-mttr mplfr Voltag gan ~ ac put oltag rc ac nput oltag r n whr rc r s total C collctor rsstanc s C mttr rsstanc of th transstor ssum that an dal dod qualnt to th bas-mttr juncton has an C mttr rsstanc of r Whn th nput oltag ( n ) s appld to th dod, n or r and r r n c C c C L n crc r rc r 5 mv 1 1 and r, rc C L 1

12 x. 9-4 Q. Dtrmn th oltag gan from th crcut blow. rc r V VCC 1 V V 0.7( V ) V r 5 mv 1 1 and r, rc C 5 mv 1 1 rc C L C 1 rc 1 1 r 5 mv C L L 1 L 1

13 as nput sstanc or Transstor Loadng n th qualnt crcut of th bas-mttr juncton, thr occurs an ffct ncras of bng bas, whr h bas F, corrspondng to th amplfcaton of bng ~ C = h F Whn h 10, bas F 10 ~ Transstor loadng ffct s nglctd and 1 Whn h 10, bas F for th prcs crcut analyss V V wth h Q CC Q F 1 Q s not so small. W apply Thnn's qualnt crcut modl

14 x. 9-5 Q. Dtrmn th oltag gan from th crcut blow. Q V VCC wth V V 0.7( V ) V r 1 Q 5 mv 1 1 rc C L C 1 rc 1 1 r 5 mv C L L Q 1 1 hf hf 1 1 h F 10 pply Thnn s qualnt crcut for th bas nput (s Ch.6b) V V V 1 1 TH CC, TH TH C TH hf V rc r V 1 5 mv 1 1 r, rc C L C L 1

15 mplfr Gans of Common-mttr mplfr Voltag gan ~ n ac put oltag ac nput oltag rc r Currnt gan ~ h f ac put currnt ac nput currnt ~ C currnt gan of th amplfr ~ C currnt gan of th transstor n h f ~ nput and put currnts ar dstrbutd or th crcut Powr gan ~ p p ac put powr p ac nput powr n

16 mplfr nput mpdanc Consdr two stag amplfr. What s a load rsstanc for th 1 st stag amplfr? That s an nput mpdanc of th nd stag amplfr, obtand from th C qualnt crcut analyss. n : nput mpdanc of th amplfr n( bas) : nput mpdanc at th bas lctrod and h r n 1 bas bas f 1 bas 1 Not h and r bas F 5 mv

17 mplfr Gan : Currnt gan ( ) Currnt gan ~ ac put currnt hf ac nput currnt n c b ~ C currnt gan of th transstor Not Thus and b n c h f c whr n h f nrc bas L n b n bas 1 h r f bas r C C L

18 mplfr Gan : Currnt gan ( ) r n c hf n basl n bas n n n n bas b bas n c b L h f b bas n c h rc f L n b c n bas 1 n c L r 1 r c hf L n bas L c n c n n n L bas b L bas h f C qualnt crcut

19 Mult-Stag mplfr Gan Calculaton 0. Chck whthr h 10 or not ~ f ys, V V ; f no, V V wth h 1. Dtrmn 5 mv. Fnd r 3. Fnd r C 4. Calculat c V L Q F 4 CC CC Q F 1 1 Q 0.7 (V) nr c 5. Calculat hf, n basl n V rc r whr, n 1 bas bas f h r 6. Calulat p T 1 3 For th cas of mult-stag amplfr, T 1 3 pt T T Not! Th nput mpdanc ( ) of th nd stag amp rplacs n th 1st stag amp. For th 1st stag, r For th nd stag, r n c C L C n c C L 1 st stag nd stag L

20 x Q. Dtrmn th oltag gan for th crcut blow. 0. Chck whthr h 10 or not f ys, V V VCC 1 V (V),1 F (V) V 1. Dtrmn 1.57 m 5 mv. Fnd r,1st Fnd r, c,1st 3 n, nd n,nd 5 6 b as,nd 5 6 hfr,nd 1.33 k r 1.05 k c,1st 3 n,nd c,1st 4. Calculat 1 53 r,1st 19.8 c,nd 5. Calculat 191 r,nd 17.4 r 3.33 k c,nd 7 L 5 mv r,nd 17.4, 6. Calculat r r T k 3.33 k ,100

21 What ab currnt/powr gan? Q. Dtrmn th currnt gan for th crcut. nr c hf n basl r T 1 n,1 st c,1st,1st hf n bas,1 st n,nd, h r 1.33 k c,1 st 3 n,nd n,nd 5 6 bas,nd 5 6 f,nd 5 mv r,nd 17.4 r r, c, 1st 3 n,nd n,1 st 1 bas,1st 1 f,1st, 1st,1 r n,1 st c,1st, 1 st hf,1st bas,1 st n,nd 3.96k 1.33k, nd f, nd T 1.05 k n, nd c,nd h r k 3.3k 3.96k 1.66 k 5 mv 19.8 h 1 r 1.66k1.05k bas,nd L pt T T 1 1 r