PNP Section 4.3,3.6

Schedule 10 9/25 Thursday PNP 11 L 9/30 Tuesday BJT in saturation 9/30 Tuesday Measure Beta of a transistor 4.3, 4.5 4.6

4.5

Modes of Operation BE\BC Forward Biased Reverse Biased Forward Biased Saturation Reverse Active Mode Reverse Biased Active 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 (N D and N A ).

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 V BE changes from 300 mV to 800 mV

Large-Signal Model of BJT Transistors (NPN) (PNP) C E C E

Experiments

Use 2n3904 npn BJT in Simulation (Error!, put 2n3904 here!)

Include 2n3904 (NPN) model