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4th April 2019, 10:09 AM  #221  
diyAudio Member
Join Date: Jan 2004
Location: Split, Croatia

Quote:
.SUBCKT VN88AFD 1 2 3 * Model Generated by MODPEX * *Copyright(c) Symmetry Design Systems* * All Rights Reserved * * UNPUBLISHED LICENSED SOFTWARE * * Contains Proprietary Information * * Which is The Property of * * SYMMETRY OR ITS LICENSORS * *Commercial Use or Resale Restricted * * by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 voltagedependent 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=1e32 +VTO=1.24222 LAMBDA=0 KP=0.410756 +CGSO=3.69374e07 CGDO=1e11 RS 8 3 3.00363 D1 3 1 MD .MODEL MD D IS=5e09 RS=0.01 N=1 BV=80 +IBV=10 EG=1.11 XTI=3 TT=0 +CJO=5.33925e11 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=1e32 N=50 +CJO=7.44807e11 VJ=0.732014 M=0.9 FC=1e08 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=1e10 N=0.4 RS=3e06 RL 5 10 1 FI2 7 9 VFI2 1 VFI2 4 0 0 EV16 10 0 9 7 1 CAP 11 10 1.5e10 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=1e10 N=0.4 .ENDS vn88afd
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4th April 2019, 11:07 PM  #222  
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Join Date: Mar 2017

IRFP340, IRFP9140 VDMOS models
Quote:
*VDMOS with subthreshold (c) Ian Hegglun Apr 2019 .model IRFP340 VDMOS (Rg=5 Vto={3.96m*(0+temp25)} Lambda=3m + Rs={35m*(1+3.5m*(0+temp25))} Kp={7.3/(1+8.8m*(0+temp25))} + Ksubthres={0.15*(1+4m*(0+temp25))} Mtriode={0.2} Rd={0.3*(1+5m*(0+temp25))} + 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+temp25))} Lambda=4m + Rs={35m*(1+3.5m*(0+temp25))} Kp={12/(1+8.8m*(0+temp25))} + Ksubthres={0.15*(1+4m*(0+temp25))} Mtriode=0.25 Rd={0.1*(1+5m*(0+temp25))} + 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 pushpull 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 pchannel to the nchannel to see how close a complement it is then it is helpful to temporarily set the Vto of the pchannel equal to the nchannel. Then you can see how close the gm's are which is what you need for wingspread gain symmetry. Cheers, 

4th April 2019, 11:23 PM  #223  
diyAudio Member
Join Date: Sep 2006

Quote:
I have never used trenchfets for a linear application and did indeed hear years ago that they are quite susceptible to second breakdownlike 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 

5th April 2019, 03:55 AM  #224  
diyAudio Member
Join Date: Mar 2017

Quote:
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 DPAK): 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 nchannel FET's and relies on the BJT's to make complements. Less trenchfets, easier to make.. Cheers, 

5th April 2019, 09:41 AM  #225 
diyAudio Member
Join Date: Jan 2004
Location: Split, Croatia

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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7th April 2019, 06:57 AM  #226  
diyAudio Member
Join Date: Mar 2017

IRF730 in VDMOS
Quote:
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={4.06m*(0+temp25)} Lambda=2m + Rs={65m*(1+3.5m*(0+temp25))} Kp={3.1/(1+8.8m*(0+temp25))} + Ksubthres={0.2*(1+4m*(0+temp25))} Mtriode={0.9} Rd={0.7*(1+5m*(0+temp25))} + 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) 

7th April 2019, 10:30 AM  #227 
diyAudio Member
Join Date: Mar 2017

VN88AFD in VDMOS
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={1.253.5m*(0+temp25)} Lambda=0m + Rs={3*(1+1m*(0+temp25))} Kp={0.41/(1+9m*(0+temp25))} + Ksubthres={0.4*(1+1m*(0+temp25))} Mtriode={1} Rd={0.1*(1+1m*(0+temp25))} + 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) 
16th April 2019, 12:22 AM  #228  
diyAudio Member
Join Date: Nov 2010
Location: Bogor

About that Kp
Quote:
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=4.0E06 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=4.0E06 N=2.4 ksubthres=107m) 

16th April 2019, 05:19 AM  #229 
diyAudio Member
Join Date: Mar 2017

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 pchannel 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 pchannel FET's than the nchannel 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? 
16th April 2019, 06:02 AM  #230  
diyAudio Member
Join Date: Nov 2010
Location: Bogor

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

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