Insulated gate bipolar transistor

1. IGBT
Insulated Gate Bipolar Transistor
N.H.D.J De Silva
ENG/13/034

2. Introduction
*Lower conduction losses
*Larger blocking voltage
*Small turn Off time
*Small turn on time
- Circuit symbol -
A three-terminal power semiconductor device primarily used as an electronic
switch which, as it was developed, came to combine high efficiency and fast
switching.

3. Basic Structure
• Cell structure similar to power MOSFET cell.
• P-region at collector end unique feature of IGBT compared to MOSFET.
• Punch-through (PT) IGBT - N+ buffer layer present.
• Non-punch-through (NPT) IGBT - N+ buffer layer absent.

4. Operations of
IGBT
1. Off State Operation
•Vgs < Vth : No inversion layer created
• Depletion layer is created along J2 ,which expands asVgs increases.
• In ‘NONPUNCHTHROUGH’ no buffer layer is present so large reverse voltage
blocking capacity.
• In ‘PUNCHTHROUGH ’ buffer layer is present shorter drift region, which
lower on-state losses. But reverse voltage blocking capacity will be low.

5. Operations of
IGBT
2. On State Operation
•Vgs > Vth , Channel is shorting Body-Drain-Drift regions.
• P+ inject holes, in to N+ region
• Holesmoves towards body region along a random path .
• Many holes will attracted by emitter metallization.
• Some holes recombines with electrons.

6. Applications
• Current rating of single IGBT can be up to 1200
volts,400Amps.
• Frequency of operation:20Khz.
• It is useful for mediumpower applications
•Ac and DC motor drives.
•Solid state relays
• High frequency signal choppers

7. Thank You