bjtlogic-4sp - Discharge path and Base-Driving circuitry 4...

1
BJT Transistors
BJT Fabrication Example
Multi-Emitter Fabrication Examples
NPN BJT

2
Ebers-Moll NPN BJT Model
) 1 e ( I I
T BE
V / V
ES BE , D
− =
) 1 e ( I I
T BC
V / V
CS BC , D
− =
BC , D R BE , D E
I I I α − =
BC , D BE , D F C
I I I − = α
C E B
I I I − =
CS R ES F
I I α α = =
S
I
Reciprocity theorem
transport saturation current
Reverse active
(RA)
Forward Reverse
Saturation
(SAT)
Forward Forward
Forward active
(FA)
Reverse Forward
Cutoff
(OFF)
Reverse Reverse
Mode BC junction BE junction
BJT Modes of Operation
Reduced models of the operation modes
(a) Cutoff
(b) Forward active
(c) Saturation (d) Reverse active
F
F
F
1 α
α
β
−
=
R
R
R 1 α
α
β
−
=
1
I I
B F C
≤
=
σ
σβ
IV Characteristics

3
Modes of Operation
Examples
β
F
= 65
I
C
, I
B
= ?
Base and emitter voltages = ?
TTL Circuit Design
Output-High Pull-up Driver