Power Device Overview

Quick Index — Other Important Power Semiconductor Devices Beyond BJT and MOSFET

Device Overview

IGBT (Insulated Gate Bipolar Transistor)

Essence

MOSFET Gate + BJT Output = Combining the Best of Both

     G (Gate, Voltage Controlled, like MOSFET)
     │
  ┌──┴──┐
  │ IG  │
  │ BT  │
  └──┬──┘
     │
     C (Collector)
     │
     E (Emitter)

Input: High-impedance voltage control (like MOSFET)
Output: Low saturation voltage drop (like BJT)

Characteristics

Applications

• Motor drives (inverter air conditioners, electric vehicles)
• Induction heating (induction cookers)
• UPS, Inverters
• High-speed rail traction, Power grids

Selection vs. MOSFET

High Frequency, Low Voltage (<200V) → MOSFET
Low Frequency, High Voltage (>600V) → IGBT
Middle Ground → SiC MOSFET is encroaching on IGBT market share

JFET (Junction Field-Effect Transistor)

Precursor to MOSFET, channel controlled by PN junction

N-channel JFET:
  Vgs ≤ 0 (Depletion mode, Normally ON)
  More negative Vgs → Narrower channel → Smaller Id

Characteristics:
- Extremely low noise (No oxide interface trap noise)
- High input impedance
- Depletion mode (Normally ON)

Applications: Low-noise preamplifiers, Audio, RF
Gradually replaced by MOSFETs, but still holds a place in low-noise applications

Thyristor (SCR)

4-layer PNPN structure, latches ON once triggered

     A (Anode)
     │
  ┌──┴──┐
  │ PNP  │
  │ NPN  │
  └──┬──┘
     │
     G (Gate → For triggering)
     │
     K (Cathode)

Trigger: Gate pulse → Latches ON
Turn-off: Current drops below holding current (Natural turn-off at AC zero-crossing)

Characteristics

• Can only control ON, cannot control OFF (Semi-controlled device)
• Low on-state voltage drop (~1.5V)
• High power (MW level)
• Frequency limited to line frequency

Applications

• Phase-controlled dimmers
• Soft starters
• High Voltage Direct Current (HVDC) transmission
• Gradually being replaced by IGBTs

Triac (Triode for Alternating Current)

Integrated body of two anti-parallel SCRs, conducts bidirectionally in AC

Applications: AC dimming, AC motor speed control, Solid State Relays (SSR)
Typical Models: BT136, BTA16

SiC (Silicon Carbide) and GaN (Gallium Nitride)

Advantages of Wide Bandgap Semiconductors

        Si       SiC      GaN
Eg:    1.12eV   3.26eV   3.4eV
Voltage Rating: Low       High      Medium
Frequency:    Low       Medium    Ultra-High
Maturity:     Most Mature Relatively Mature Developing

SiC MOSFET

Advantages:
- Voltage rating 650V~3.3kV
- Extremely low switching losses
- High-temperature operation (>200°C)
- Small temperature coefficient of Rds(on)

Disadvantages:
- Expensive (3~5x more than Si MOSFET)
- Strict gate drive requirements (Narrow Vgs range)
- High body diode Vf (~3V)

Applications: EV traction inverters, OBCs, PV inverters

GaN HEMT

Advantages:
- Extremely fast switching (MHz range)
- No body diode (No reverse recovery)
- High power density in small packages

Disadvantages:
- Low voltage rating (<650V)
- Fragile gate (Voltage rating ±6V!)
- ESD sensitive

Applications: Mobile phone fast chargers (65W/120W GaN chargers), LiDAR, 5G base stations

Quick Selection Guide

Keywords: IGBT, JFET, SCR, Thyristor, Triac, SiC, GaN, Wide Bandgap, Power Devices