types of transistors

Types of Transistors

• Transistor Classifications:

  • BJT (Bipolar Junction Transistor)

  • FET (Field Effect Transistor)

Bipolar Junction Transistor (BJT)

• Configuration Types:

  • NPN

  • PNP (NPN preferred)

• Functionality:

  • Has two PN junctions

  • Current controlled device

Field Effect Transistor (FET)

• Characteristics:

  • Three-terminal unipolar device

  • Voltage controlled device

  • High input impedance (in Mega Ohms)

  • Low power consumption and heat dissipation

  • Lower noise levels than BJTs

• Key Features:

  • Gain characterized by transconductance: $g<em>m = \frac{\Delta I</em>{out}}{\Delta V_{in}}$

  • Output impedance is low

• Advantages Over BJT:

  • Unipolar vs. bipolar

  • Voltage driven vs. current driven

  • Better thermal stability

FET Terminal Structure

• Terminals:

  • Gate (analogous to Base)

  • Source (analogous to Emitter)

  • Drain (analogous to Collector)

• Current Designation:

  • Current into Source: $I_S$

  • Current into Gate: $I_G$

  • Current out of Drain: $I_D$

• Drain to Source Voltage:

  • Designated as $V_{DS}$

Types of FET

• Major Types:

  • JFET

  • MOSFET

Overview of Upcoming Content

• Detailed discussion on JFET and MOSFET in subsequent chapters.