The Bipolar Junction Transistor

Cross Section of Integrated Circuit npn Transistor

Modes of Operation

Forward-ActiveB-E junction is forward biasedB-C junction is reverse biased

SaturationB-E and B-C junctions are forward biased

Cut-OffB-E and B-C junctions are reverse biased

Inverse-Active (or Reverse-Active)B-E junction is reverse biasedB-C junction is forward biased

npn BJT in Forward-Active

Electrons and Holes in npn BJT

Electrons and Holes in pnp BJT

Circuit Symbols and Current Conventions

Current Relationships

=

=

+=

=

+=

1

)1(

EC

BE

BC

BCE

iiii

iiiii

Common-Emitter Configurations

Common-Base Configuration

Current-Voltage Characteristics of a Common-Base Circuit

Current-Voltage Characteristics of a Common-Emitter Circuit

Early Voltage/Finite Output Resistance

Effect of Collector-Base Breakdown on Common Base I-V Characteristics

Effect of Collector-Base Breakdown on Common Emitter I-V Characteristics

DC Equivalent Circuit for npn Common Emitter

DC Equivalent Circuit for pnp Common Emitter

Load Line

Problem-Solving Technique:Bipolar DC Analysis

1. Assume that the transistor is biased in forward active modea. VBE = VBE(on), IB > 0, & IC = IB

2. Analyze linear circuit.3. Evaluate the resulting state of transistor.

a. If VCE > VCE(sat), assumption is correctb. If IB < 0, transistor likely in cutoffc. If VCE < 0, transistor likely in saturation

4. If initial assumption is incorrect, make new assumption and return to Step 2.

Voltage Transfer Characteristic for npn Circuit

Voltage Transfer Characteristic for pnp Circuit

Digital Logic

Inverter NOR gate

Bipolar Inverter as Amplifier

Effect of Improper Biasing on Amplified Signal Waveform

Single Base Resistor Biasing

Common Emitter with Voltage Divider Biasing and Emitter Resistor

CCTH VRRRV )/([ 212 +=

Integrated Circuit Biasing

21

1

+==

III QC

Multistage Cascade Transistor Circuit

The Bipolar Junction TransistorCross Section of Integrated Circuit npn TransistorModes of Operationnpn BJT in Forward-ActiveElectrons and Holes in npn BJTElectrons and Holes in pnp BJTCircuit Symbols and Current Conventions Current RelationshipsCommon-Emitter ConfigurationsCommon-Base ConfigurationCurrent-Voltage Characteristics of a Common-Base CircuitCurrent-Voltage Characteristics of a Common-Emitter CircuitEarly Voltage/Finite Output ResistanceEffect of Collector-Base Breakdown on Common Base I-V CharacteristicsEffect of Collector-Base Breakdown on Common Emitter I-V CharacteristicsDC Equivalent Circuit for npn Common EmitterDC Equivalent Circuit for pnp Common EmitterLoad LineProblem-Solving Technique:Bipolar DC AnalysisVoltage Transfer Characteristic for npn CircuitVoltage Transfer Characteristic for pnp CircuitDigital LogicBipolar Inverter as AmplifierEffect of Improper Biasing on Amplified Signal WaveformSingle Base Resistor BiasingCommon Emitter with Voltage Divider Biasing and Emitter ResistorIntegrated Circuit BiasingMultistage Cascade Transistor Circuit