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THEORY OF OPERATION
E-5 E-5
VANTAGE® 500
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 in Figure E.5 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 ter-
minal of the IGBT may be connected to a voltage sup-
ply; 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, the
device is capable of conducting current. A voltage sup-
ply connected to the drain terminal will allow the IGBT
to conduct and supply current to circuit components
coupled to the source. Current will flow through the
conducting IGBT to downstream components as long
as the positive gate signal is present. This is similar to
turning ON a light switch.
FIGURE E.5 – 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
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