EE PRO for TI-89, 92 Plus
Equations - Solid State Devices
88
α
r Ir
Is
⋅ =
Eq. 27.5.7
The last three equations define ICE0 and ICB0 in terms of
αα
f ,
αα
r,
β
f and Ir0.
ICB
r
f
Ir
0
1
0
= −
⋅
⋅
α α
b
g
Eq. 27.5.8
ICE
ICB
f
0
0
1
=
⋅
+
β
b
g
Eq. 27.5.9
ICE
Ir
f
r
f
0
0 1
1
=
⋅ −
⋅
−
α α
α
b
g
Eq. 27.5.10
Example 27.5.1 -
A junction transistor has a forward and reverse
α
of 0.98 and 0.10 respectively. The collector
current is 10.8 mA while the forward current is 12.5 mA. respectively. Compute the base, saturation and reverse
currents, in addition to the forward and the reverse
β
.
Display (Upper-half)
Display (Lower-half)
Solution -
The second through sixth equations are needed to solve this problem. Select these using the highlight bar
and pressing the
¸
key. Press
„
to display the input screen, enter all the known variables and press
„
to solve
the equation set. The computed results are shown in the screen displays above.
-PQYP8CTKCDNGU
αα
H
α
T
+%
AO#
++H
AO#
%QORWVGF4GUWNVU
β
H
β
T
+$
µ
#
+T
A#
+U
A#
27.6 Ideal Currents - pnp
The four equations in this set form the basis of transistor action resulting in
emitter, base and collector currents in a pnp transistor. The first three equations
show the emitter, collector and base currents IE, IC, and IB in terms of emitter
base area A1, diffusion coefficients DE, DB, and DC, the minority carrier densities
nE, pB, and nC, emitter and collector diffusion lengths LE and LC, base width
WB, emitter-base and collector base voltages VEB and VCB, base collection junction A2 and temperature TT. The
last equation shows the relationship between
α
, DB, pB, WB, DE, nE and LE. The corresponding equations for an
npn transistor can be derived from this equation set by proper use of sign conventions.
IE
q A
DE nE
LE
DB pB
WB
e
q A
DB
WB
pB e
q VEB
k TT
q VCB
k TT
= ⋅ ⋅
⋅
+
⋅
F
HG
I
KJ
⋅
−
F
HG
I
KJ
− ⋅
⋅
⋅
−
F
HG
I
KJ
⋅
⋅
⋅
⋅
1
1
2
1
Eq. 27.6.1
IC
q A DB pB
WB
e
q A
DC nnC
LC
DB pB
WB
e
q VEB
k TT
q VCB
k TT
= ⋅ ⋅
⋅
⋅
−
F
HG
I
KJ
− ⋅
⋅
⋅
+
⋅
F
HG
I
KJ
⋅
−
F
HG
I
KJ
⋅
⋅
⋅
⋅
1
1
2
1
Eq. 27.6.2