bjt, bipolar junction transisor
DESCRIPTION
Base Current Controls Output current. BJT, Bipolar Junction Transisor. Bollen. BJT transistorman Transistor types Bipolar Junction Transistor BJT models parameters water model NPN and PNP operation modes switch open switch closed. BJT linear, controlled current source - PowerPoint PPT PresentationTRANSCRIPT
1
BJT, Bipolar Junction Transisor
Bollen
Base CurrentBase Current
ControlsControls
Output currentOutput current
2
AGENDA
Bollen
BJT transistormanTransistor typesBipolar Junction TransistorBJT modelsparameterswater modelNPN and PNPoperation modesswitch openswitch closed
BJTlinear, controlled current sourceactive operationcharacteristicsDC input characteristicsac input characteristicsBJT DC biasing circuitsbase biasbase bias + collector feedbackbase bias + emitter feedbackvoltage divider
3
BJT, transistor man
Bollen
4
TransistorTypes
Bollen
Output currentOutput current controlled controlled
by by input currentinput current
Output currentOutput current controlledcontrolled
by by input voltageinput voltage
BJT ==
Bipolar Junction Bipolar Junction TransistorTransistor
FET ==
Field Effect TransistorField Effect Transistor
5
BJT, Bipolar Junction Transisor
Bollen
BE ForwardBE Forward bias, bias, BC ReverseBC Reverse bias bias
So So lowlow ohmic ohmic highhigh ohmic ohmic
TransistorTransistor == TranTransfersfer ReResistorsistor
6
BJT, Bipolar Junction Transisor
Bollen
Emitter Emitter = Sent = Sent electronselectrons
BaseBase = Base = Base
CollectorCollector = Get = Get electrons electrons
7
BJT, Models
Bollen
8
BJT, parameters
Bollen
9
BJT, Water model
Bollen
10
BJT, Water model
Bollen
11
BJT, NPN and PNP
Bollen
12
BJT, Operation modes
Bollen
Cut-off and Cut-off and saturation;saturation;
BJT is used as a BJT is used as a switchswitch
Active operationActive operation
Quiecent Point;Quiecent Point;
BJT is used as a BJT is used as a
controlled controlled
current source,current source,
or or analog amplifieranalog amplifier
13
BJT, Switch open
Bollen
14
BJT, Switch closed
Bollen
15
BJT, Lineair, controlled current source
Bollen
16
BJT, active operation
Bollen
17
BJT, characteristics
Bollen
DCDC model model acac model model
DCDC model; Vbe = 0V7 Ube, Uce, Ic, Ib, Ie model; Vbe = 0V7 Ube, Uce, Ic, Ib, Ie CapitalsCapitals
acac model; re = 26mV/Ie ube, uce, ic, ib, ie model; re = 26mV/Ie ube, uce, ic, ib, ie Low Low casescases
18
BJT, DC input characteristics
Bollen
Vbe = 0V7
19
BJT, AC input characteristics
Bollen
re = 26mV/Ic
The dynamic resistor can be calculated by the DC current
Ic
20
BJT, characteristics
Bollen
21
BJT, DC biasing circuits
Bollen
A base biasA base bias
B base bias + emitter feedbackB base bias + emitter feedback
C base bias + collector feedbackC base bias + collector feedback
D voltage dividerD voltage divider
22
BJT, base bias, introduction
Bollen
Base current determined by Vcc, Rb and Vbe
23
BJT, base bias
Bollen
cc Rb beV U U
cc b b beV I R U
c bI I Calculate Ib and then Ic
Ic directly dependent on ß variation
So, for stability a “bad” circuit
24
BJT, base bias load line
Bollen
Load line is the loading of the transistor seen from Uce (>0V7)
Vcc and Rc determines the; “open voltage” and the “short circuit current”
Q-point = Quiecient
point= Working point
25
BJT, base bias load line
Bollen
Load line is the loading of the transistor seen from Uce (>0V7)
Vcc and Rc determines the; “open voltage” and the “short circuit current”
Reliable circuit= Q-point
stability
26
BJT, base bias load line
Bollen
Vce always > 0V7BC junction
REVERSE
If Rc too big, transistor in saturation; then;
27
BJT, base bias load line
Bollen
Vce always > 0V7BC junction
REVERSE
If Vcc too small, transistor in saturation; then;
28
BJT, base bias example
Bollen
Calculate;
Ib, IcURc, Uc, Uce
Draw output caracteristic
Calculate now;
Uce if ß = 40How many % did Uce
ChangeIb = 47 uA, Ic = 2,35 mA, URc = 5,17 V, Uc = 6,83 V, Uce = 6,83 VUce (for ß = 40) = 7,86 Ξ 15 %
29
BJT, base bias example
Bollen
Ib = 33 uA, Ic = 2,9 mA URc = 7,9 V, Uc = 8,1 V
Rb = 282,5 kΩ, Ic = 3,2 mA,
Rc = 1,855 kΩ
30
BJT, base bias example
Bollen
ß = 200, VRc = 8,8 VVcc = 16 VRb = 765 kΩ
31
BJT, base bias + emitter feedback
Bollen
Base current determined by Vcc, Rb, Vbe and Ve
More stable for ß variations, than base bias.
32
BJT, base bias + emitter feedback
Bollen
Always calculate in the smallest current Ib !!
Recc Rb beV U U U
Re1cc b b be bV I R U I U
Rc c cV I R
c cc c cV V I R
e e eV I R
ce c eV V V
33
BJT, base bias + emitter feedback
Bollen
Load line is the loading of the transistor seen from Uce (>0V7)
Vcc, Rc and Re determines the; “open voltage” and the “short circuit current”
34
BJT, base bias + emitter feedback example
Bollen
Calculate;
Ib, IcURc, Uc, Ue, Uce
Draw output caracteristic
Ib = 6,2 uA, Ic = 0,74 mA, URc = 8,9 V, Uc = 7,1 V, Ue =-0,9 V, Uce = 8,0 V
35
BJT, base bias + emitter feedback example
Bollen
Calculate;
Ib, IeURe, Ue, Uce
Draw output caracteristic
Ib = 24 uA, Ie = 2,9 mA, URc = 3,5 V, Ue = -2,5 V, Uce = 2,5 V
36
BJT, base bias + collector/emitter feedback
Bollen
If Ic > then Uc < then Ib <
If Ic > then Uc <and Ue > then Ib <
37
BJT, base bias + collector feedback
Bollen
cc Rc Rb beV U U U
1cc b c b b beV I R I R U
Always calculate in the smallest current Ib !!
The current through Rc is not Ic but Ic + Ib,
so (β+1)Ib !!!
If Ic rises for any reason, then Uc falls and
also Ib decreases, so then Ic decreases
38
BJT, base bias collector feedback example
Bollen
Calculate;
Ib, ß, Ic
Draw output caracteristic
Ib = 13 uA, ß = 196, Ic = 2,5 mA
39
BJT, base bias collector/emitter feedback
Bollen
Recc Rc Rb beV U U U U
1
1
cc b c
b b
be
b e
V I R
I R
U
I R
Always calculate in the smallest current Ib !!
40
BJT, base bias collector/emitter feedback ex
Bollen
Calculate;
Ib, IeURc, Uc, Ue, Uce
Draw output caracteristic
Ib = 11,8 uA, Ie = 1,1 mA
URc = 5,2 V, Uc = 4,8 V
Ue = 1,3 V, Uce = 3,5 V
41
BJT, voltage divider
Bollen
Vb is a stable voltage - 0,7 V =
so Ve is a stable voltageIe is determined by Ve/ Re
Ic = Ie . ß/(ß+1)
Ic is very stable and nearly independent to ß
variation, as long as ß is BIG in value
2 methods of calculating Ic - neglegting Ib, use voltage divider - not neglecting Ib and use thevenin
42
BJT, voltage divider, neglect Ib
Bollen
2
1 2b cc
RV V
R R
0 7e bV V V
ee
e
VI
R
1c eI I
So neglegt Ib to R2, or in general Ri >> R2In practice 10 times bigger
43
BJT, voltage divider, exact, thevenin
Bollen
Thevenin resistance
R1 // R2 62k // 9k1= 7k9
Thevenin voltage 2
1 2th cc
RV V
R R
9 116 2 0
62 9 1th
kV V
k k
44
BJT, voltage divider, exact, thevenin
Bollen
2V0
7k9
1th b th be b eV I R V I R
2,0 7 9 0,7 80 1 0,68b bI k I k Ib = 20 uA
45
BJT, voltage divider, example
Bollen
Thevenin resistance = 6k8
Thevenin voltage = 3V1
Ib = 18,8 uAIc = 2,25 mAre = 11,5 ΩURc = 7V4Uc = 10V6Ue = 2V3Uce = 5V1
46
BJT, voltage divider, example
Bollen
Thevenin resistance = 255k
Thevenin voltage = 0V0
Ib = 14,3 uAIc = 1,9 mAre = 14 ΩURc = 17V3Uc = 0V7Ue = -3V7Uce = 4V4
47
BJT
Bollen
48
BJT
Bollen