THEORY OF OPERATION
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INSULATED GATE BIPOLAR TRANSISTOR (IGBT) OPERATION
An IGBT is a type of transistor. IGBT are semiconduc- tors well suited for high frequency switching and high current applications.
Example A in Figure E.6 shows an IGBT in 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.
Example 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 con- nected to the drain terminal will allow the IGBT to con- duct and supply current to the 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.
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FIGURE E.6 – IGBT
POSITIVE
VOLTAGE
APPLIED
| GATE |
| GATE |
SOURCE | SOURCE | ||
n + | n + | n + | n + |
p | BODY REGION | p | BODY REGION |
n - | DRAIN DRIFT REGION | n - | DRAIN DRIFT REGION |
n + | BUFFER LAYER | n + | BUFFER LAYER |
p + | INJECTING LAYER | p + | INJECTING LAYER |
DRAIN |
| DRAIN |
|
A. PASSIVE |
| B. ACTIVE |
|
