Transcript BJT in Saturation Mode

PNP
Section 4.3,3.6
Schedule
10
9/25
Thursday PNP
4.3, 4.54.6
11
9/30
Tuesday
BJT in saturation
4.5
L
9/30
Tuesday
Measure Beta of a transistor
Modes of Operation
BE\BC
Forward Biased
Reverse Biased
Forward Biased
Saturation
Active
Reverse Biased
Reverse Active
Mode
Cut-Off
Applications:
1. Saturation and cut-off mode are used in digital circuits.
2. Active mode is used in the amplifier design.
Collector Voltage Versus
Base Current
VBE versus IB
VCE Versus IB
Base Current
electron current
Hole current
The proportional of hole current and electron current
is determined by dopants (ND and NA).
Even though the presence of holes are minimized, a small
number of holes still must enter through the base.
Operation of an NPN
Transistor in the Active Region
Electrons are injected
into the B; holes to the E.
Electrons
are injected
into the BC junction
Electrons
are swept across
the reversed biased BC
BJT Current
Assumption:
BEJ: Forward Biased
BCJ: Reverse Biased
Extension of a PNP transistor
(NPN transistor)
(PNP transistor)
1. Emitter-base junction is forward
biased.
2. Holes are injected into the base.
3. Base-collector junction is reverse
Biased.
4. Injected holes in the base is swept
across the base-collector junction by
the electric field.
Large Signal Model of a BJT
Called “large” signal model
because this model is
applicable even if VBE
changes from 300 mV to 800 mV
Large-Signal Model of BJT
Transistors
(NPN)
C
E
(PNP)
C
E
Experiments
Use 2n3904 npn BJT in
Simulation
(Error!, put 2n3904 here!)
Include 2n3904 (NPN) model