Post on 01-Mar-2016
description
5. (BJTs)
,
, . , .
1947 John Bardeen and Walter Brattain, William Shockley, @ Bell Labs () (Nobel prize 1956)
1954 Texas Instruments ().
166
5.1
() ()
, . , .
To on, off,
on, off
. on, off
(wafers) ().
167
()
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5.2
168
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- .
(interfacing) .
.
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p-n-p n-p-n. -- . .
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, . , .
(Emitter)
(Base) (
) (Collector)
( ) ( )
169
npn- Transistor pnp- Transistor
p pn
n np
, . , .
e- ( ) .
170
5.3 Transistor
n np
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( ) CB
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0,7V 0,3V
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173
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, (, ...)
(J) (Jc). . , , , .
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5.4 Transistor
( )
EB,CB
EB,CB
EB CB
174
( e-
)
p pnn np
B
CE
B
CE
B
CE
B
CE
a. b. c.
+
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+
-B
CE
B
CE
+
-+
- B
CE
, . , .
>0,7V ( ) e-
e- ( ).
e- .
e- .
175
5.5
+
-+
- B
CE
, . , .
CB
. npn: . pnp : .
(npn: e ) .
CB (e )
. . .
176
q(V0+VCB)
q(V0-VBE)
BE
CB
, . , .
177
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>0,7V ( ) e-
e-
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B
CE
>0,7V
IB=IE-IC
, . , .
179
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CEp
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>0,7V
IB=IE-IC
e- ( ), e- .
.
, . , .
5.6
-pnp
.
IE IpE ( ) InE ( ). IpE/ InE JE p n- .
. p-n-p . .
IE =IpE +InE, JE JC . IPC1 IpE IpE - IPC1 . .
180
, . , .
npn
181
To JT
, . , .
182
JC Ic IC0. : InCo p n IpCo n p JC. :
:
.
p-n-p IE IC0 IC.
n-p-n .
(2) IC0 (IE =0) :
pCOnCOC0 III
C CO pC1 C0 EI I I I I
, . , .
(large-signal current gain) . 0,9-0,995. IE, VCB .
(2) . . IC0 I-V . I0 IC0 V VC JC p n . :
VC VT (4) (2).
183
C TV VC E COI I -I 1 e
0I
II
E
COC
, . , .
5.7 dc
DC
:
adc = IC / O
, adc
adc .
' ( EB, BC). rb. (50-150)
() rb . , IBrb .
rb . rb .
184
C
, . , .
5.8 Early-
. . . , . , JE () Jc . WB WB WB =WB-W, W .
185
, . , .
Early.
VCB : VCB ( )
. |VCB| IpC1 ( 2).
H (pn) . pn 0 d V0. JE o IE |VCB|.
VCB WB . Punch-through.
186
, . , .
5.9
187
, -- . - VCB.
T : |VCB| IE Early VEB. |VCB|.
. VBE 1V .
, . , .
5.10
188
(active region)
JC . IE =0. IC0 (mA nA Ge Si ). IE0 I IC (2). VCB IE. Early (. ) 0,5% |IC| |VCB|.
(saturation region)
VCB =0 IE =0 J , JC .
J C .
IC . pnp, JC .
I J JC (cutoff region).
active region
, . , .
5.11 Tran(sfer Re)sistor
189
. Tran(sfer Re)sistor. .
:BE VBB BC VCC
IB , IC IE ( IC = IE 1)
rE = ac
IE = Vin/rE (Ohms Law)
Vout = ICRC IERC
out Vin
VA
V
E C C CV
E E E E
I R R RA
I r r r
, . , .
O .
.
. VBE 0,7V .
, .
,
190
RB
n
n
p
+
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+
- RC
VBB
VCC
VCB
VBE
VCE
+
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- - - -- - - -- - - -- - - -- - - -- - - -- - - -- - - -- - - -- - - -
>0,7V
5.12
, . , .
ICE / IBE (TRANSFERCHARACTERISTIC). hfe
, . DC transistor, (dc CE) ,
dc = IC /
transistor 5% , , IB. , dc 20., dc 50 300. transistor dc 1000.
191
5.13 dc
, . , .
192
5.14
. ( =50, C=10mA).
( Kirchhoff): IE=IC+IB ,
IC= IC0-IE : -1
I
-1
II BC0C
-1
BC0C II1I
IB>>IC0 IC=IB. IC VCE. (. ). Early.
, . , .
IE=IC+IB IC :
193
E B
C C dc dc
dcdc
dc
I I 1 11 1
I I a
a
1
a = IC/IE < 1
b = IC/IB
, . , .
=100
IB= 10
IC = 100(10 ) = 1 mA
H VCE
(
)
VBB IB= 20
IC = 100(20 ) = 2 mA
VCE
VCE , ;
( ) :
VCE= VCB + VBE = VCB + 0,7 V = 0 + 0,7V =0,7V. H VCB 0- ( )
194
( ), VCE 1 V, .
, .
, . , .
IB=0 IB= IE-IC IE= IC.
(.. 0,9 ) IC=10 IC0 . IB=0 JE.
JC JE
.
( volt) VCE=VBE-VBC, VCE
IC VCE
VCE 0,7V
.
IC : IC = dc
VCE ( ) .
195
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5.15 DC
(cutoff)
= 0 C 0
Maximum VCE=VCC Q ( )
.
.
I(sat), ' , . RC VCC IC(sat) =IC(max)
200
CE satV : CC CE sat CC
C sat
C C
c CC CE
C sat
B sat
V V VI
R R
I 0 V V
II
, . , .
1mV peak
R110k
RL2.2k
RC3.6k
RE1k
VCC+10V
dc=200
5.16
dc , . (=200)
To IB . ,
transistor. :
ac , ac. (-1800) ac :
2
1 2
1 8.TH B CCR
V V V VR R
1 8 1 8. .ac dcV V
T acV V V
1 1.BE B E EV V V V V 6 04.C CC C CV V I R V
201
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202
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203
. .
JC
JE Jc . .
, JC Ico. B = 0 c = (+1) Ico.
L :
+1. n-p-n Ic-VCE . B. B0. c B.
IC=(+1)(C0+IL)
5.17
, . , .
, .
0.7v . .
, .
. +1 :
204
5.18
, . , .
. - , .
VB . VB .
5.19
VB 0.7V ( < VC), VE = VB0.7 V.
: VB + VB; VE VE + VE = VB + VB 0.7 V. VE = VB, VE/VB= 1. ( ) , .
, . .
205
, . , .
; : IE = IB. , : IE + IE = (IB + IB),
IE/IB=
(100), . . buffer . ;
206
, . , .
VBE 0.6 Volts . , , .
VBE 0.7 Volts , - . , VBE=0.7 Volts .
:
207
VBE(Volts) VCE (Volts)
< 0.6
VCE=0=C=0
0.7 VCB>0 (npn) IC=hFEIB 0.7 VCE=0 IB ICSat / hFE
:
1. VBE 0,7 Volts , . 2. VCE .3. VBE, .
, . , .
5.1
208
dc . :
=(VBB-VBE)/RB= (10V-0.7V)/1.5M=6.2
To dc dc :
To transistor 2N3904 dc =125. dc ;
C dc BI I 125 6 2 A 0 775mA. .
CE CC C CV V I R 20 0 775mA 5k 16 1V, ,
dc - :
, . , .
5.2
209
To transistor 2N4401 dc = 80. dc
:
:
dc transistor.
20 mA - - 30 V, RB.
CC
C
V 30V20mA
R 1 5k.
CCV 30V
, . , .
5.3
210
IC VCE Q RB = 390 k dc = 80;
CE CC C CV V I R 30V 6mA 1 5k 21V.
CC BEB
B
V V 30V 0 7VI 75 1 A
R 390k
..
:
C dc BI I 80 75 1 6mA. :
:
Q 6mA 21 V
RB Q ' dc . RB Q .
, . , .
5.4
211
, LED, transistor ; dc = 150, Vin transistor ; LED 2 V.
transistor , , VCE . ' 1 k LED. transistor
To dc , transistor ,
, transistor ,
CC LED
LED C sat C
C
V V 20V 2VI I 18mA
R 1k
in B B BEV I R V 0 12mA 47k 0 7V 6 34V. . .
C sat
B sat
dc
I 18mAI 0 12mA
150.
, . , .
212
(=100, IC0=20nA=2*10
-15mA).
VBB npn . .
. Kirchoff : -5+200IB+VBE=0.
( ) VBE=0,7V :
: IC00. :
IB IC RC . 3K VCB .
mA0215.0200
7,05IB
V85,27,01015,23V 0VVI310
CB
BECBC
5.5
, . , .
213
R=50K. =100 IB IC.
Kirchoff : -5+50IB+0,8=0 IB=4.2/50=0,084mA
: -10+3IC+0,2=0 IC=9,8/3=3,27mA
IB :
IB=0,084> IBmin= 0,033mA .
CB minI 3,27
I 0,033mA100
5.6