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Better power MOSFET models in LTSpice
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Old 4th April 2019, 10:09 AM   #221
aparatusonitus is offline aparatusonitus  Croatia
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Quote:
Originally Posted by haiqu View Post
What's the closest model to the old Siliconix VMP series VMOS parts?
You can try an VN88AFD...it's the same m-fet in different housing as Siliconix 2N6658 aka VMP-4 or VMP-12 iirc...

.SUBCKT VN88AFD 1 2 3
* Model Generated by MODPEX *
*Copyright(c) Symmetry Design Systems*
* All Rights Reserved *
* UNPUBLISHED LICENSED SOFTWARE *
* Contains Proprietary Information *
* Which is The Property of *
* SYMMETRY OR ITS LICENSORS *
*Commercial Use or Resale Restricted *
* by Symmetry License Agreement *
* Model generated on Sep 8, 97
* MODEL FORMAT: SPICE3
* Symmetry POWER MOS Model (Version 1.0)
* External Node Designations
* Node 1 -> Drain
* Node 2 -> Gate
* Node 3 -> Source
M1 9 7 8 8 MM L=100u W=100u
* Default values used in MM:
* The voltage-dependent capacitances are
* not included. Other default values are:
* RS=0 RD=0 LD=0 CBD=0 CBS=0 CGBO=0
.MODEL MM NMOS LEVEL=1 IS=1e-32
+VTO=1.24222 LAMBDA=0 KP=0.410756
+CGSO=3.69374e-07 CGDO=1e-11
RS 8 3 3.00363
D1 3 1 MD
.MODEL MD D IS=5e-09 RS=0.01 N=1 BV=80
+IBV=10 EG=1.11 XTI=3 TT=0
+CJO=5.33925e-11 VJ=5 M=0.834582 FC=0.5
RDS 3 1 1.15e+07
RD 9 1 0.0001
RG 2 7 1.26706
D2 4 5 MD1
* Default values used in MD1:
* RS=0 EG=1.11 XTI=3.0 TT=0
* BV=infinite IBV=1mA
.MODEL MD1 D IS=1e-32 N=50
+CJO=7.44807e-11 VJ=0.732014 M=0.9 FC=1e-08
D3 0 5 MD2
* Default values used in MD2:
* EG=1.11 XTI=3.0 TT=0 CJO=0
* BV=infinite IBV=1mA
.MODEL MD2 D IS=1e-10 N=0.4 RS=3e-06
RL 5 10 1
FI2 7 9 VFI2 -1
VFI2 4 0 0
EV16 10 0 9 7 1
CAP 11 10 1.5e-10
FI1 7 9 VFI1 -1
VFI1 11 6 0
RCAP 6 10 1
D4 0 6 MD3
* Default values used in MD3:
* EG=1.11 XTI=3.0 TT=0 CJO=0
* RS=0 BV=infinite IBV=1mA
.MODEL MD3 D IS=1e-10 N=0.4
.ENDS vn88afd
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Old 4th April 2019, 11:07 PM   #222
IanHegglun is offline IanHegglun  Australia
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Default IRFP340, IRFP9140 VDMOS models

Quote:
Originally Posted by aparatusonitus View Post
...It would be very nice indeed if you could the same for IRFP9140 (for less then +/-40VDC supply) and IRFP340 (for less then +/-80VDC supply)...
Here they are:

*VDMOS with subthreshold (c) Ian Hegglun Apr 2019
.model IRFP340 VDMOS (Rg=5 Vto={3.9-6m*(0+temp-25)} Lambda=3m
+ Rs={35m*(1+3.5m*(0+temp-25))} Kp={7.3/(1+8.8m*(0+temp-25))}
+ Ksubthres={0.15*(1+4m*(0+temp-25))} Mtriode={0.2} Rd={0.3*(1+5m*(0+temp-25))}
+ Cgdmax={1.7n} Cgdmin={20p} a={0.35} Cgs={1.4n} Cjo={1n} Tnom=temp
+ m=0.75 VJ=5 IS=1n N=1.3 Rb=0.1 Vds=400 Ron=0.5 Qg=62nC mfg=VishIH1904)
*
*VDMOS with subthreshold (c) Ian Hegglun Apr 2019
.model IRFP9140 VDMOS (pchan Rg=6 Vto={(-3.76+6m*(0+temp-25))} Lambda=4m
+ Rs={35m*(1+3.5m*(0+temp-25))} Kp={12/(1+8.8m*(0+temp-25))}
+ Ksubthres={0.15*(1+4m*(0+temp-25))} Mtriode=0.25 Rd={0.1*(1+5m*(0+temp-25))}
+ Cgdmax={2.3n} Cgdmin={20p} a={0.35} Cgs={1.4n} Cjo={590p} Tnom=Temp
+ m=0.5 Vj=0.75 N=3 Is=10p Rb=0.08 Vds=-100 Ron=0.2 Qg=61nC mfg=VishIH1904)

I used Vishay datasheets. Jigs are attached in case you want to see.

I use gm values for Kp and some only give a "min" gm but I use "typ" gm for my Kp's. Some give "min" and "typ" gm so I use this ratio to estimate the "typ" gm when not given. This suggests you can expect up to +/-30% variations in gm values from the same supplier for dMOSFET's. BTW Exicon lateral's seem to be about +/-10% over decades and Hitachi/Renesas equivalents are within +/-20% of the Exicon's over decades.

It means random use of of p- and n- MOSFET's like the IRFP240 and IRFP9240 is a hit and miss affair in practice. Models can only indicate typical marching. You can't generalize abot how well MOSFET's like the IRFP240 and IRFP9240 are good complements just from their models either.

If you look at the SGS IRF640 and the Vishay IRF640, the SGS typ gm is 30% higher.

That's why there are a quite large range of Kp's (and gm's) between VDMOS model's of the same part number for dMOSFET's.

Another variation between VDMOS model's of the same part number is the Vto value. This does not affect gain symmetry in a push-pull amplifier so I thought it might help to use Bob Cordell's VDMOS model Vto's for the same part numbers (if Bob has one available). For the IRFP240 he uses 4.0V and for the IRFP9240 he uses -3.76V. But be aware that real amplifiers, paralleled MOSFET's of the same polarity will not have perfectly matched Vto's like your simulations, and it would help to select parts to match MOSFET Vto's of the same polarity (you can use lower value source R's that run cooler which improves reliability).

If you are using my jigs then when comparing a p-channel to the n-channel to see how close a complement it is then it is helpful to temporarily set the Vto of the p-channel equal to the n-channel. Then you can see how close the gm's are which is what you need for wingspread gain symmetry.

Cheers,
Attached Files
File Type: zip IRFP340-IRFP9140-VDMOS.zip (6.3 KB, 18 views)
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Old 4th April 2019, 11:23 PM   #223
Bob Cordell is offline Bob Cordell  United States
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Quote:
Originally Posted by IanHegglun View Post
Hi aparatusonitus,

If you are interested in symmetry, did you see my recent Echo amp circuit?
Spice model for Russian KP903A JFET?
I thought of it for LU1014D's. But now propose 5th generation trench MOSFET's. Most are aware generations after the IRF640 generation can't be used in linear mode direct off the +/-40-80V rails due to thermal hot spots (Spirito effect). But using them as Rush pairs with RET power transistors you get true symmetry and a wider better crossover region. Still just simulations.

Cheers,
Hi Ian,

I have never used trenchfets for a linear application and did indeed hear years ago that they are quite susceptible to second breakdown-like effects. Not surprising, as they are optimized for switching power supplies where they ideally should not be dissipating much in the linear region anyway.

Regarding your suggestion of using them in Rush pairs with BJT power transistors, are there actually any trenchfets available in P channel? Most SMPS use only N channel devices.

Cheers,
Bob
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Old 5th April 2019, 03:55 AM   #224
IanHegglun is offline IanHegglun  Australia
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Quote:
Originally Posted by Bob Cordell View Post
...Regarding your suggestion of using them in Rush pairs with BJT power transistors, are there actually any trenchfets available in P channel? Most SMPS use only N channel devices.
Hi Bob,

Nice to have you pop in. I see from your book thread you are now proof reading. I am looking forward to your 2nd Ed.

There are a few P trenchfets that match to N trenchfets in terms of gm for Rush pairs. I did a search 18 months ago for my Alpha and Charlie Rush amps and bought samples to try. But I left those designs for other things and have yet to return and complete them. Some pairs I have to try are (mostly D-PAK):
MTD5867 (n,60V,20A,26mR)+FDD5614 (p,60V,15A,0.1R)
NTD4909 (n,30V,40A,7mR) + IFD50P04 (p,40V,50A,9mR)
IRFU024 (n,60V,10A,0.1R) + IFQU17P06 (p,60V,12A,0.13R) or IPLU014 (n,60V,8A,0.18R)
MTD3055, MTD2955 (60V,12A) Not sure about if still available or if trenchfet.

The 'Alpha' amp IansAlphaAmp - Google Drive was bench tested with IRF640/9640 as a 50W common source "Pass" amp for current drive of a speaker. It uses p+n pairs with BJT cascode. Differences between the upper Rush FET pair and the lower Rush FET pair cancel out giving low DC offset drift and no need to match p & n MOSFET's.

The 'Charlie' amp IansCharlieAmp - Google Drive was simulated and a PCB was started. It is a 50W Diamond follower with an upper Rush trench FET pair and a lower Rush trench FET and a dMOSFET cascode. There are 14 MOSFET's and 10 are trenchfets, of these 4 need a heatsink and another 6 need to track their temperature. With 10 small SMD DPAK power transistors in contact with a heatsink it was a challenge to design a PCB for this amp that was not a pain to assemble. You can see photos of how it.can be done with only two main bolts two plates. And the dMOSFET's have spreader plates. For a 200W version I duplicate the PCB and then parallel it.

The 'Echo' amp does not need p+n channel FET's since it uses two n-channel FET's and relies on the BJT's to make complements. Less trenchfets, easier to make..

Cheers,
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Old 5th April 2019, 09:41 AM   #225
aparatusonitus is offline aparatusonitus  Croatia
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Ian, I can't thank you enough for all the leg (and brain) work you have done...my hat's off to you, sir!
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Old 7th April 2019, 06:57 AM   #226
IanHegglun is offline IanHegglun  Australia
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Default IRF730 in VDMOS

Quote:
Originally Posted by Cartman222 View Post
....Does anyone have an LTspice model for an IRF730 n-Channel Power MOSFET?...
Hi Cartman,

aparatusonitus posted a MODPEX model here Better power MOSFET models in LTSpice

I converted it to VDMOS (my jigs attached to compare them). Almost identical except the VDMOS has subthreshold conduction.

*VDMOS with subthreshold (c) Ian Hegglun Apr 2019
.model IRF730 VDMOS (Rg=5 Vto={4.0-6m*(0+temp-25)} Lambda=2m
+ Rs={65m*(1+3.5m*(0+temp-25))} Kp={3.1/(1+8.8m*(0+temp-25))}
+ Ksubthres={0.2*(1+4m*(0+temp-25))} Mtriode={0.9} Rd={0.7*(1+5m*(0+temp-25))}
+ Cgdmax=1.2n Cgdmin=5p a=0.25 Cgs=500p Cjo=300p Tnom=temp
+ m=0.75 VJ=5 IS=1n N=1.3 Rb=0.01 Vds=400 Ron=1 Qg=38nC mfg=VishIH1904)
Attached Files
File Type: zip IRFP730-VDMOS-extract-jigs.zip (5.3 KB, 9 views)
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Old 7th April 2019, 10:30 AM   #227
IanHegglun is offline IanHegglun  Australia
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Default VN88AFD in VDMOS

Quote:
Originally Posted by haiqu View Post
What's the closest model to the old Siliconix ....
Hi haiqu,

Here's the MODPEX converted to VDMOS for LTspice. Better charge plot.to the Vishay datasheet (jigs attached). Better subthreshold region.

*VDMOS with subthreshold (c) Ian Hegglun Apr 2019
.model VN88AFD VDMOS (Rg=1 Vto={1.25-3.5m*(0+temp-25)} Lambda=0m
+ Rs={3*(1+1m*(0+temp-25))} Kp={0.41/(1+9m*(0+temp-25))}
+ Ksubthres={0.4*(1+1m*(0+temp-25))} Mtriode={1} Rd={0.1*(1+1m*(0+temp-25))}
+ Cgdmax=10p Cgdmin=0.7p a=1 Cgs=35p Cjo=40p Tnom=temp
+ m=0.75 VJ=5 IS=1p N=1.3 Rb=0.1 Vds=80 Ron=4 Qg=0.5nC mfg=VishIH1904)
Attached Files
File Type: zip VN88AFD-VDMOS_07-Apr-2019.zip (4.7 KB, 6 views)
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Old 16th April 2019, 12:22 AM   #228
indra1 is offline indra1  Indonesia
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Default About that Kp

Quote:
Originally Posted by IanHegglun View Post
... I use gm values for Kp and some only give a "min" gm but I use "typ" gm for my Kp's. ...
I had incorrect second harmonic phase on simulation of IRFP240 - IRFP9240 follower which may be caused by Kp parameter of the IRF9240 model being larger than the IRFP240 which does not reflect the typically higher Gm of the IRFP240 compared to IRFP9240 at a certain Id.

Found a youtube video How to model a MOSFET using a datasheet which shows a relation of :
Gm = sqrt(2 * Kp * Id)
hence
Kp = Gm**2 / (2 * Id)

From Harris and Intersil datasheets Gm vs Id curve, calculated Kp was plugged into Bob Cordell's model and I have better result with respect to phase of second harmonic.

Here is the modified model I now use. I am no expert in spice, so please correct me if you see any error.
Code:
* IRFP240C VDMOS copyright Cordell Audio December 20, 2014
* Modified by Indra1 April 10, 2019
.model irfp240C VDMOS(nchan Vto=4.0 Kp=5.042 Lambda=0.0032 Rs=0.01 Rd=0.1 
+Rds=1e7 Cgdmax=1100p Cgdmin=80p a=0.35 Cgs=1275p Cjo=3000p m=0.75 VJ=2.5 
+IS=4.0E-06 N=2.4 ksubthres=190m)
*
*
* IRFP9140C VDMOS   copyright Cordell Audio December 6, 2010
* Modified by Indra1 April 10, 2019
.model irfp9140C VDMOS(pchan Vto=-3.75746 Kp=2.667 Lambda=0.004 Rs=50m Rd=200m
+Rds=1e7 Cgdmax=750p Cgdmin=130p a=0.26 Cgs=1200p Cjo=2300p m=0.68 VJ=2.5 
+IS=76p N=2.4 ksubthres=0.107)
*
*
* IRFP9240C VDMOS copyright Cordell Audio December 20, 2014
* Modified by Indra1 April 10, 2019
.model irfp9240C VDMOS(pchan Vto=-3.76 Kp=3.226 Lambda=0.004 Rs=0.064 Rd=0.1 
+Rds=1e7 Cgdmax=700p Cgdmin=110p a=0.26 Cgs=1400p Cjo=2070p m=0.68 VJ=2.5 
+IS=4.0E-06 N=2.4 ksubthres=107m)
Attached Images
File Type: gif Gm IRFP240 Harris.gif (10.9 KB, 163 views)
File Type: gif Gm IRFP9240 Intersil.gif (24.7 KB, 164 views)
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Old 16th April 2019, 05:19 AM   #229
IanHegglun is offline IanHegglun  Australia
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Hi indra1,

Your approach is correct. The equation for Kp using gm or gfs neglects Rs degeneration, which is OK for starting values. The video you mention does not cover adding Rs. When you add Rs the value of Kp needs to be higher. I have a white paper (Pt.1) here VDMOS - PAK2 devo

Using gm@Id is a useful short cut to get Kp because you don't need to solve simultaneous equations like in the video.

I usually use Vishay datasheets. They don't have Gfs vs Id plots for the IRFP240/9240 but they do give gfs at one Id which is enough to calculate the starting Kp. EG

Vishay IRFP240 the gfs=6.9 A/V at 12A so Kp=2 (min) and using typ=1.3min gives Kp=2.6.typ and no Rs.yet.

Vishay IRFP9240 the gfs=4.2 A/V at 7.2A so Kp=3.6 (min) and using typ=1.3min gives Kp=4.7.typ and no Rs yet.

The Vishay datasheets give higher Kp's for the p-channel by a factor of 1.8 times. That's why Bob Cordell and my models end up with a Kp of 5 or 6 for the IRFP240 and 9 for the IRFP9240.once Rs is accounted for.

If your amplifier has a lower Kp for p-channel FET's than the n-channel FET's and you want your simulations to match your amp then by all means tailor the models to match your FET's.

BTW What brand of FET's are you using?
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Old 16th April 2019, 06:02 AM   #230
indra1 is offline indra1  Indonesia
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Quote:
Originally Posted by IanHegglun View Post
... I usually use Vishay datasheets. They don't have Gfs vs Id plots for the IRFP240/9240 but they do give gfs at one Id which is enough to calculate the starting Kp. ...
Thank you for the link Ian.
No wonder, the problem seems to stem from min Gfs value of the Vishay data.
Folks at the Pass forum are using a lot of IRFP240/9x40 and in most cases, the actual Gfs of the N is higher than the P. Attached are the measured Id/Vgs curves of typical Vishay parts made by another member, published in Pass forum a few years ago.
Attached Images
File Type: jpg IRFP 240_9240a.jpg (272.3 KB, 142 views)
File Type: png IRFP240_9140 vishay.png (16.3 KB, 155 views)

Last edited by indra1; 16th April 2019 at 06:28 AM.
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