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)

 

Main difference = 1 component instead of 2.

 

An IGBT can generally handle much higher power with fewer losses, but sacrifices switching speed.

 

Here is a white paper on the subject: http://www.irf.com/technical-info/whitepaper/choosewisely.pdf

John

 

a bipolar transistor with an insulated gate instead of a base connection.

 

a bipolar transistor with an insulated gate instead of a base connection.

Not exactly. There is a full BJT and a full FET built into an IGBT.

Here is a (simplified) internal circuit diagram (Left: equivalent, Right: effective):

 

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.

 

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

 

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.

 

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.

 

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...