Electronic Devices and Circuits

5.

Bipolar Junction Transistors (BJTs)

5.1.

BJT Structure and Basic Operation

5.1.1.

Physical Structure

5.1.1.1.

NPN Transistor Construction

5.1.1.2.

PNP Transistor Construction

5.1.1.3.

Base Width Considerations

5.1.2.

Transistor Action

5.1.2.1.

Emitter Injection

5.1.2.2.

5.1.2.3.

Collector Collection

5.1.3.

Current Components

5.1.3.1.

Emitter Current

5.1.3.2.

5.1.3.3.

Collector Current

5.1.3.4.

Current Relationships

5.2.

BJT Current Gains

5.2.1.

Common-Base Current Gain (α)

5.2.1.1.

Definition and Typical Values

5.2.1.2.

Alpha Cutoff Frequency

5.2.2.

Common-Emitter Current Gain (β)

5.2.2.1.

Definition and Typical Values

5.2.2.2.

Beta Cutoff Frequency

5.2.2.3.

Relationship between α and β

5.3.

BJT Operating Regions

5.3.1.

5.3.1.1.

Forward-Active Mode

5.3.1.2.

Amplification Characteristics

5.3.2.

Saturation Region

5.3.2.1.

Both Junctions Forward Biased

5.3.2.2.

Switch ON State

5.3.3.

5.3.3.1.

Both Junctions Reverse Biased

5.3.3.2.

Switch OFF State

5.3.4.

Inverse Active Region

5.3.4.1.

Reverse Operation Mode

5.4.

BJT Configurations and Characteristics

5.4.1.

Common-Base Configuration

5.4.1.1.

Input Characteristics

5.4.1.2.

Output Characteristics

5.4.1.3.

Current Gain and Input Resistance

5.4.2.

Common-Emitter Configuration

5.4.2.1.

Input Characteristics

5.4.2.2.

Output Characteristics

5.4.2.3.

Current Gain and Input Resistance

5.4.3.

Common-Collector Configuration

5.4.3.1.

Input Characteristics

5.4.3.2.

Output Characteristics

5.4.3.3.

Voltage Gain and Input Resistance

5.5.

BJT Biasing Circuits

5.5.1.

Fixed Bias Configuration

5.5.1.1.

Circuit Analysis

5.5.1.2.

Stability Issues

5.5.2.

Emitter Bias Configuration

5.5.2.1.

Improved Stability

5.5.2.2.

Circuit Analysis

5.5.3.

Voltage Divider Bias

5.5.3.1.

Most Common Biasing Method

5.5.3.2.

Design Considerations

5.5.3.3.

Stability Analysis

5.5.4.

Collector Feedback Bias

5.5.4.1.

Self-Biasing Action

5.5.4.2.

Circuit Analysis

5.5.5.

Emitter Follower Bias

5.6.

5.6.1.

Stability Factors

5.6.1.1.

Temperature Effects

5.6.1.2.

Beta Variation Effects

5.6.2.

Thermal Runaway

5.6.2.1.

Causes and Prevention

5.6.3.

Compensation Techniques

5.7.

BJT as an Amplifier

5.7.1.

DC and AC Load Lines

5.7.1.1.

Q-Point Selection

5.7.1.2.

Maximum Signal Swing

5.7.2.

Small-Signal Operation

5.7.2.1.

Linear Amplification

5.7.2.2.

Distortion Considerations

5.7.3.

Large-Signal Operation

5.7.3.1.

Clipping and Saturation

5.8.

BJT Small-Signal Models

5.8.1.

Hybrid-π Model

5.8.1.1.

Model Parameters

5.8.1.2.

Equivalent Circuit

5.8.1.3.

Parameter Extraction

5.8.2.

5.8.2.1.

Alternative Representation

5.8.2.2.

Model Parameters

5.8.3.

h-Parameter Model

5.8.3.1.

Two-Port Network Representation

5.8.3.2.

h-Parameter Definitions

5.8.3.3.

Measurement Techniques

5.9.

BJT Switching Characteristics

5.9.1.

Switching Times

5.9.1.1.

5.9.1.2.

5.9.1.3.

5.9.1.4.

5.9.2.

Switching Speed Limitations

5.9.3.

Speed-Up Techniques

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