Little clarity please? IGBT?

Thread Starter

Tonyr1084

Joined Sep 24, 2015
5,871
I have this device. An Insulated Gate B ? ? ? T ? ? ? Insulated gate field effect transistor. What's the B all about?

I know what it is but I don't understand the IGBT, the BT part of it in particular.GP7NC60HD.jpg
 

mtonge

Joined Apr 19, 2016
93
From Wikipedia:
An insulated-gate bipolar transistor (IGBT) is 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.

Sounds interesting, I'll have to read on to see if it is something I can use too.
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
5,871
So is it more like a B(ipolar)J(unction)T(transistor) or a FET? I recognize the gate is insulated, so it can't be a BJT, there's no "Junction" between the Base & Emitter. Or collector for that fact.

It comes off a dead garage door opener. I believe it powered the motor. Relays set the motor direction. Up to 160 VDC. I've been scrapping parts off the board. I have seven relays, single pole double throw type. Not sure of the coil voltage though. I suppose I'll get around to googling it eventually.
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
5,871
Does this page from out eBook make things more clear?
"In essence, the IGFET controls the base current of a BJT, which handles the main load current between collector and emitter. This way, there is extremely high current gain (since the insulated gate of the IGFET draws practically no current from the control circuitry), but the collector-to-emitter voltage drop during full conduction is as low as that of an ordinary BJT." Quoted from Bertus' posting.

Thanks. That absolutely clears it up. Now I understand the nature of "Hybrid of a MOSFET and a BJT."
 

ian field

Joined Oct 27, 2012
6,539
So is it more like a B(ipolar)J(unction)T(transistor) or a FET? I recognize the gate is insulated, so it can't be a BJT, there's no "Junction" between the Base & Emitter. Or collector for that fact.

.
Its both - 2 devices on one die. A MOSFET and a bipolar transistor connected together.
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
5,871
Yes, Ian, thanks. Came to that conclusion.

Thanks all who clarified this for me.

HEY ALL - RUN OUT AND GET SOME BULK CHOCOLATE AND SOME STRAWBERRIES AND HAVE IT READY FOR THIS EVENING. MELT THE CHOCOLATE IN A SMALL CROCK POT AND DIP THE STRAWBERRIES IN THE CHOCOLATE. USE BABMOO SKEWERS OR ROUND TOOTHPICKS TO HOLD THE STRAWBERRIES.
 

ian field

Joined Oct 27, 2012
6,539
think of it as a Darlington where the input is a MOSFET gate (high impedance voltage controlled) and the output is a BJT (actually better for very high currents than MOSFET).
Its not a Darlington - its different - that's why it has a different name; The Szicklai pair, in this case a hybrid Szicklai pair with a MOSFET and a BJT.

The Darlington is 2 DC coupled common emitter stages - the IGBT is a common source MOSFET driving an emitter follower BJT.
 

ian field

Joined Oct 27, 2012
6,539
think of it as a Darlington where the input is a MOSFET gate (high impedance voltage controlled) and the output is a BJT (actually better for very high currents than MOSFET).
Not necessarily - The output stage BJT can't saturate, so the on time losses aren't *ALL THAT* less than the RDSon of the older MOSFETs it was developed to replace.

There have been big advances in reducing RDSon in modern MOSFETs, so the IGBT isn't quite the great wonder it once was. The common emitter output stage also restricts switching speed - for some applications; the IGBT is just too slow.
 
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