IGBT output impedance

darkfenriz · 7th December 2004, 09:53 PM

Hallo
is output imedance of IGBT low or high compared to bjt and MOSFET??
just starting interesting IGBTs and cannot find much practical data- only sructure theory.

waiting for answers
cheers

Sch3mat1c · 8th December 2004, 12:59 AM

AFAIK, it's a BJT with a MOSFET in front of it, sorta, so it doesn't take any power to switch massively. But that doesn't explain why they are slow, they only come up to 600V (at least what I've seen at Mouser) and supposedly have NO tolerance for anything out of limits.

Don't know what kind of linearity they have, if any. Only used for switching big stuffs AFAIK...

Tim

hjelm · 8th December 2004, 06:37 AM

Does this help?
600V 30A IGBP

You can derive the output impedance from the datasheet but the problem is that it is increasing at low Vce values, i think.

At 30A the Vce drop is ~2.1 v which is about 70mohm.

darkfenriz · 8th December 2004, 07:16 AM

thank you
i found somewhere this schematic (hope I don't harm enyone's copyright or anything) and was thinking of common emmiter or SE mode
what do you think?

hjelm · 8th December 2004, 08:25 AM

Building anything with IGBP devices is way over my head.

Although i do think the schematic is interesting especially the two feedback loops. I wouldn't consider myself competent enough to design those.

darkfenriz · 9th December 2004, 09:34 PM

another words
do you think IGBT may work good as a follower?

johnnyx · 9th December 2004, 10:14 PM

I have read that there are special considerations required to operate IGBT' as a follower, such as you see in many amp designs. They can latch-up, due to a parasitic NPNP thyristor style construction. I saw a design once, probably in Wireless World or Electronics World, that used a biasing arrangement to prevent this occuring.

OTOH JLL Hood has used them in amplifier designs, so maybe this problem is exagerated. I would do a bit more background reading first before trying them.

I see them used a lot in the latest power inverters for motor control. In that application, they appear to have many advantages, efficiency being the most obvious, in that the size has shrunk for the same power.

hjelm · 10th December 2004, 06:21 AM

Saw this on peufeu's site. Maybe some ideas?

It includes latchup protection.
IGBP amp

johnnyx · 10th December 2004, 04:46 PM

That is very probably the one I was thinking of.

darkfenriz · 12th December 2004, 11:15 AM

I'm just looking for lowest output impedance possible
igbts seem tempting with low emmiter resistance combined with voltage driving, don't they?

7th December 2004, 09:53 PM	#1
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	IGBT output impedance Hallo is output imedance of IGBT low or high compared to bjt and MOSFET?? just starting interesting IGBTs and cannot find much practical data- only sructure theory. waiting for answers cheers

8th December 2004, 12:59 AM	#2
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	AFAIK, it's a BJT with a MOSFET in front of it, sorta, so it doesn't take any power to switch massively. But that doesn't explain why they are slow, they only come up to 600V (at least what I've seen at Mouser) and supposedly have NO tolerance for anything out of limits. Don't know what kind of linearity they have, if any. Only used for switching big stuffs AFAIK... Tim __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

8th December 2004, 06:37 AM	#3
hjelm diyAudio Member Join Date: Nov 2003 Location: Västerås	Does this help? 600V 30A IGBP You can derive the output impedance from the datasheet but the problem is that it is increasing at low Vce values, i think. At 30A the Vce drop is ~2.1 v which is about 70mohm. __________________ Hjelm

8th December 2004, 08:25 AM	#5
hjelm diyAudio Member Join Date: Nov 2003 Location: Västerås	Building anything with IGBP devices is way over my head. Although i do think the schematic is interesting especially the two feedback loops. I wouldn't consider myself competent enough to design those. __________________ Hjelm

10th December 2004, 06:21 AM	#8
hjelm diyAudio Member Join Date: Nov 2003 Location: Västerås	Saw this on peufeu's site. Maybe some ideas? It includes latchup protection. IGBP amp __________________ Hjelm


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9th December 2004, 09:34 PM	#6
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	another words do you think IGBT may work good as a follower?

9th December 2004, 10:14 PM	#7
johnnyx diyAudio Member Join Date: Jan 2004 Location: manchester	I have read that there are special considerations required to operate IGBT' as a follower, such as you see in many amp designs. They can latch-up, due to a parasitic NPNP thyristor style construction. I saw a design once, probably in Wireless World or Electronics World, that used a biasing arrangement to prevent this occuring. OTOH JLL Hood has used them in amplifier designs, so maybe this problem is exagerated. I would do a bit more background reading first before trying them. I see them used a lot in the latest power inverters for motor control. In that application, they appear to have many advantages, efficiency being the most obvious, in that the size has shrunk for the same power.

10th December 2004, 04:46 PM	#9
johnnyx diyAudio Member Join Date: Jan 2004 Location: manchester	That is very probably the one I was thinking of.

12th December 2004, 11:15 AM	#10
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	I'm just looking for lowest output impedance possible igbts seem tempting with low emmiter resistance combined with voltage driving, don't they?

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