Joshua's Docs - Transistors Cheat Sheet
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Disclaimer: I am not an EE, nor have I taken any EE classes. This is a cheatsheet, for myself, to remember some of the simple basics of transistors.

Resources

Here are some helpful resources for learning more about the basics of transistors:

What & Link Type
Zeeshan Ali, AIKTC School of Engineering: Introduction to Transistors Slide Deck
Zeeshan Ali, AIKTC School of Engineering: Transistor Types Slide Deck
ElectronicsTutorials: Transistor Series
- Summary (👍)
- MOSFET as a Switch
Guide
Circuit Digest: Different Types of Transistors Guide
Espruino: MOSFETs
- Schematics section
Guide (Intro)

Different Types of Transistors

  • BJT (Bipolar Junction Transistor)

    • Control: Current
    • Pins:

      • Base (B)
      • Collector (C)
      • Emitter (E)
    • Configurations:

      • NPN
      • PNP
  • FET (Field Effect Transistor)

    • Control: Voltage
    • Pins

      • Drain (D)
      • Gate (G)
      • Source (S)
    • Configurations:

      • MOSFET

        • Depletion Mode:

          • N-Channel
          • P-Channel
        • Enhancement mode:

          • N-Channel
          • P-Channel
      • JFET

        • Depletion Mode:

          • N-Channel
          • P-Channel
      • OFET
      • NOMFET
  • IGBT (Insulated Gate Bipolar Transistor)

    • This could also be considered a subset of FET

Comparing Types of Transistors

So, between some of the major types, what are the significant differences, in a broad practical sense? As in, why might you pick one over the other?

Type Control Pros Cons
BJT Current - More robust (in comparison to MOSFET)
- Often tolerant of a greater voltage range
- Less expensive
- Thermal runaway
- Slower switching
- Typically handles less current
FET - MOSFET Voltage - Extremely high input resistance on Gate, means that there is very little current draw
- Fast Switching speeds
- The high input resistance means they are extremely sensitive to ESD, and are more easily damaged by it
FET - JFET Voltage - Less vulnerable to ESD, compared to MOSFET
- Often cheaper than MOSFETs
- Consumes more current than MOSFET
- Only available in Depletion Mode

Other comparisons you might find helpful

Sub-Type Breakdown

Type Config Pins Usage Differentiator Symbol
BJT NPN B,C,E - Small current at base, allows large current from collector to emitter.
- Base needs to be positive relative to Emitter.
BJT NPN symbol
BJT PNP B,C,E - Small current at base, allows large current from emitter to collector.
- Base needs to be negative relative to Emitter.
BJT PNP symbol
FET -> JFET N-Channel (Depletion Mode) D,G,S - "On", by default.
- Negative voltage at Gate (relative to Source), turns off / increases resistance / reduces current between Source and Drain (the channel).
JFET N-Channel Labelled
FET -> JFET P-Channel (Depletion Mode) D,G,S - "On", by default.
- Positive voltage at Gate (relative to Source), turns off / increases resistance / reduces current between Source and Drain (the channel).
JFET P-dep symbol (case)
FET -> MOSFET N-Channel (Depletion Mode) D,G,S (* B) - "On", by default.
- Negative Voltage at Gate (relative to Source), turns off / increases resistance / reduces current between Source and Drain (the channel).
N-Channel Depletion Mode MOSFET Symbol
FET -> MOSFET P-Channel (Depletion Mode) D,G,S (* B) - "On", by default.
- Positive Voltage at Gate (relative to Source), turns off / increases resistance / reduces current between Source and Drain (the channel).
P-Channel Depletion Mode MOSFET Symbol
FET -> MOSFET N-Channel (Enhancement Mode) D,G,S (* B) - "Off", by default
- Positive Voltage at Gate (relative to Source), turns on / decreases resistance between Source and Drain (the channel).
N-Channel Enhancement Mode MOSFET Symbol
FET -> MOSFET P-Channel (Enhancement Mode) D,G,S (* B) - "Off", by default
- Negative Voltage at Gate (relative to Source), turns on / decreases resistance between Source and Drain (the channel).
P-Channel Enhancement Mode MOSFET Symbol

* = Sometimes MOSFETs will include a fourth terminal, B. This is often referred to as Body or Substrate, and sometimes is not broken out, but rather connected internally.

Markdown Source Last Updated:
Sat Jul 18 2020 18:43:51 GMT+0000 (Coordinated Universal Time)
Markdown Source Created:
Thu Jun 18 2020 20:13:25 GMT+0000 (Coordinated Universal Time)
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