INSULATED GATE BIPOLAR
TRANSISTOR (IGBT) OPERATION
An IGBT is a type of transistor. IGBTs are semicon-
ductors well suited for high frequency switching and
high current applications.
Drawing A shows an IGBT in a passive mode. There is
no gate signal, zero volts relative to the source, and
therefore, no current flow. The drain terminal of the
IGBT may be connected to a voltage supply; but since
there is no conduction, the circuit will not supply current
to components connected to the source. The circuit is
turned off like a light switch in the OFF position.
Drawing B shows the IGBT in an active mode. When
the gate signal, a positive DC voltage relative to the
source, is applied to the gate terminal of the IGBT, it
is capable of conducting current. A voltage supply
connected to the drain terminal will allow the IGBT to
conduct and supply current to circuit components cou-
pled to the source. Current will flow through the con-
ducting IGBT to downstream components as long as
the positive gate signal is present. This is similar to
turning ON a light switch.
E-11
E-11
THEORY OF OPERATION
POWER WAVE 455/R
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FIGURE E.9 – IGBT OPERATION
DRAIN
SOURCE
GATE
INJECTING LAYER
BUFFER LAYER
DRAIN DRIFT REGION
BODY REGION
p +
n +
n -
p
n +
n +
DRAIN
SOURCE
GATE
INJECTING LAYER
BUFFER LAYER
DRAIN DRIFT REGION
BODY REGION
p +
n +
n -
p
n +
n +
POSITIVE
VOLTAGE
APPLIED
B. ACTIVE
A. PASSIVE