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I have a question that in motor driving application, by using power MOSFET, it must be in saturation region, is this right? And for IGBT, in which region it must be to act as a switching device?

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by using power MOSFET, it must be in saturation region, is this right ?

No, when a MOSFET is in saturation it will determine (regulate) the amount of current that flows. Due to this regulation the MOSFET will get very hot. For driving a motor this is bad as you want the motor to determine the current by applying the full supply voltage across it. For that you need the MOSFET to be in linear mode (also called triode mode).

You want the MOSFET to act as a switch and then you must use it in linear mode.

Probably you're confused by Bipolar transistors because for bipolars the mode where the transistor acts as a switch is called saturation mode.

Since the main switching device in a IGBT is a Bipolar transistor, it will operate in saturation mode.

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  • \$\begingroup\$ This is the annoying part about MOSFETs, that the saturation region doesn't behave as someone would think something saturated would do. - Similar to the H note in instruments, that should be B. \$\endgroup\$ – Harry Svensson Oct 9 '18 at 13:41
  • \$\begingroup\$ In linear region the MOSFETs will behave like a resistor and in saturation it will act like a current source, is this correct ? Can you explain about the regions in the IGBT, I'm kinda confused about thier names. \$\endgroup\$ – Electronics newbie Oct 9 '18 at 13:55
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    \$\begingroup\$ @Electronicsnewbie The naming of the regions doesn't make sense (in my opinion) so instead, ask Bimpelrekkie how you should drive the gates of the IBGT and MOSFETs. This way you will understand everything clearly and you won't destroy anything. Weird names for regions will only confuse everyone, including me and you. \$\endgroup\$ – Harry Svensson Oct 9 '18 at 14:51
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    \$\begingroup\$ Note to OP: For a BJT, "saturation" means "current saturation"; it's the condition where the thing is saturated with current and the collector-emitter voltage is as low as it'll go. For a MOSFET, "saturation" means "voltage saturation": it's the condition where the drain-source voltage is (mostly) regulated by the gate-source voltage. From a circuits point of view they are opposite conditions. I'm not sure what the mode is called for IGBTs, but you want the one where the thing is turned fully on, and the C-E voltage is a minimum. \$\endgroup\$ – TimWescott Oct 9 '18 at 14:52
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    \$\begingroup\$ @Harry Svensson Yea verily! Just drive the thing hard, and don't worry about what the books say the mode is named. \$\endgroup\$ – TimWescott Oct 9 '18 at 14:53

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