IGBT

Thread Starter

onceinalifetim

Joined Feb 9, 2014
27
I know that IGBT is combine together with MOSFET and BJT. the common feature is a gate, a collector and a n emitter..

so what is the main different between IGBT vs (MOSFET & BJT)
 

KL7AJ

Joined Nov 4, 2008
2,225
I know that IGBT is combine together with MOSFET and BJT. the common feature is a gate, a collector and a n emitter..

so what is the main different between IGBT vs (MOSFET & BJT)
The IGBT has nearly zero "on" resistance, which makes it ideal for switching applications, plus the input impedance is very high, so driving power is minimal.
 

DerStrom8

Joined Feb 20, 2011
2,390
The IGBT has nearly zero "on" resistance, which makes it ideal for switching applications, plus the input impedance is very high, so driving power is minimal.
I'm just going to add on to this. I was going to mention it this morning but I was in a rush to get to work, and didn't have enough time.

FETs are effectively voltage-controlled resistors. Their on-resistance changes depending on the voltage applied to the gate. If you pass a current through it (from drain to source), your power loss will be (according to Ohm's Law):



Notice that the power increases exponentially with current, thus the losses will increase significantly at higher currents. On the other hand, an IGBT does not act as a voltage-controlled resistor. As KL7AJ mentioned, it has a very low on-resistance (generally a few milliohms). Its losses are really only determined by the voltage drop of the silicon itself. Therefore, the losses will be (again, according to Ohm's Law):



As you can see, the power loss does NOT increase exponentially with current, making it much more efficient (less lossy) at higher currents.

Hope this clears some things up.

Regards,
Matt
 

clickclack

Joined Sep 30, 2014
5
At lower voltages where the diode drop is a significant part of the operating voltage isn't the FET generally superior though?

I'm working on a project for harvesting and bucking up power from a 12V solar panel right now and keeping diode drops out of the current path is a concern on the input voltage side. I've looked at a lot of solar designs doing research and I don't recall seeing any IGBTs at all.
 

DerStrom8

Joined Feb 20, 2011
2,390
At lower voltages where the diode drop is a significant part of the operating voltage isn't the FET generally superior though?

I'm working on a project for harvesting and bucking up power from a 12V solar panel right now and keeping diode drops out of the current path is a concern on the input voltage side. I've looked at a lot of solar designs doing research and I don't recall seeing any IGBTs at all.
Yes, at lower power levels MOSFETs are definitely superior. They are faster and smaller. IGBTs are generally used for large motor drivers, which can see very high currents.
 

cmartinez

Joined Jan 17, 2007
6,992
Check this video, it shows how to use a MOSFET as an extremely efficient diode with a very low voltage drop:

Also, the narrator has a knack for keeping it interesting...
 
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