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Si-C MOSFET body diode

Started by Harry D October 13, 2014
So I am testing a C2M002512D body diode, see attached.  I have two test
setups at 25C with different results.
1, Short G to S  and apply -1.0ma of current from D to S;  measure Vds
= -1.07V
2, Apply G=-5V, S=0 and apply -1.0mA of current D to S; measure Vds= -2.40V

Look at attached spec, sheet #4. Looks like Vgs can modulate the body diode.

Cheers,   HarryD 

On Mon, 13 Oct 2014 17:22:34 -0700, "Harry D" <harryd@tdsystems.org>
wrote:

>So I am testing a C2M002512D body diode, see attached. I have two test >setups at 25C with different results.
>1, Short G to S and apply -1.0ma of current from D to S; measure Vds >= -1.07V >2, Apply G=-5V, S=0 and apply -1.0mA of current D to S; measure Vds= -2.40V > >Look at attached spec, sheet #4. Looks like Vgs can modulate the body diode. > >Cheers, HarryD
I don't recognize that part, but the data sheet for the C2M0040120D shows a lot of such "body diode" modulation. I'm thinking there is no actual body diode, just a jfet sort of turn-on of the main channel at negative drain voltage. Tacky. (I can't see attachments in this ng.) I've considered using SiC fets, but we're in the high speed biz, and they have huge internal gate series resistances, which will slow them down. I've noticed that other non-silicon fets (mesfets, phemts) have no equivalent of a body diode. They behave like jfets. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
In article <m1hqc6$6u5$1@dont-email.me>, harryd@tdsystems.org says...
> > So I am testing a C2M002512D body diode, see attached. I have two test > setups at 25C with different results. > 1, Short G to S and apply -1.0ma of current from D to S; measure Vds > = -1.07V > 2, Apply G=-5V, S=0 and apply -1.0mA of current D to S; measure Vds= -2.40V > > Look at attached spec, sheet #4. Looks like Vgs can modulate the body diode. > > Cheers, HarryD
I see a couple problems: 1. There is no attached spec that I can see.. 2. I can't find that PN on the net to reference. Jamie
You can tell it's a body diode by the shitty recovery time.  If it were a 
gate modulated thing, it would have no recovery time.

SiC has worse mobility than Si I think, which leads to poorer performance 
in related parameters (higher series resistance, slower recovery).  The 
higher bandgap and breakdown voltage mean you still get a better figure of 
merit, for certain applications like high voltage switching.

Note that the "Vbe" or Vf of the PN junction is proportionally higher 
(about 2.4V at 1mA for a device this size...) because of the bandgap. 
This is true of SiC BJTs, of course.

Tim

-- 
Seven Transistor Labs
Electrical Engineering Consultation
Website: http://seventransistorlabs.com

"Harry D" <harryd@tdsystems.org> wrote in message 
news:m1hqc6$6u5$1@dont-email.me...
> So I am testing a C2M002512D body diode, see attached. I have two test > setups at 25C with different results. > 1, Short G to S and apply -1.0ma of current from D to S; measure Vds > = -1.07V > 2, Apply G=-5V, S=0 and apply -1.0mA of current D to S; measure > Vds= -2.40V > > Look at attached spec, sheet #4. Looks like Vgs can modulate the body > diode. > > Cheers, HarryD
On 14/10/14 02.22, Harry D wrote:
> So I am testing a C2M002512D body diode, see attached. I have two test > setups at 25C with different results. > 1, Short G to S and apply -1.0ma of current from D to S; measure Vds > = -1.07V > 2, Apply G=-5V, S=0 and apply -1.0mA of current D to S; measure Vds= -2.40V > > Look at attached spec, sheet #4. Looks like Vgs can modulate the body > diode. > > Cheers, HarryD
Hi! Did you mean: C2M0025120D: http://www.digikey.dk/product-search/en?vendor=0&keywords=C2M002512 http://www.cree.com/~/media/Files/Cree/Power/Data%20Sheets/C2M0025120D.pdf In that case, figure 8,9,10 on page 4 documents it. How does C2M0025120D measure at Vgs= +1, +2V ? Glenn
On Tue, 14 Oct 2014 14:19:24 +0200, Glenn <glenn2233@gmail.com> wrote:

>On 14/10/14 02.22, Harry D wrote: >> So I am testing a C2M002512D body diode, see attached. I have two test >> setups at 25C with different results. >> 1, Short G to S and apply -1.0ma of current from D to S; measure Vds >> = -1.07V >> 2, Apply G=-5V, S=0 and apply -1.0mA of current D to S; measure Vds= -2.40V >> >> Look at attached spec, sheet #4. Looks like Vgs can modulate the body >> diode. >> >> Cheers, HarryD > >Hi! > >Did you mean: > >C2M0025120D: >http://www.digikey.dk/product-search/en?vendor=0&keywords=C2M002512 >http://www.cree.com/~/media/Files/Cree/Power/Data%20Sheets/C2M0025120D.pdf > >In that case, figure 8,9,10 on page 4 documents it. > >How does C2M0025120D measure at Vgs= +1, +2V ?
The "body diode" drop should go down! -- John Larkin Highland Technology, Inc jlarkin att highlandtechnology dott com http://www.highlandtechnology.com