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24th October 2015, 04:45 PM  #111 
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Join Date: Aug 2006
Location: Texas

The VDMOS equations in LTSpice aren't quite the same as the EKV equations. This does mean the LTspice VDMOS model isn't quite as good at modeling the subthreshold region as the EKV model, although it is still a giant step forward.
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5th December 2015, 03:50 AM  #112  
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Join Date: Sep 2013

Quote:
Your values are identical for N and P
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5th December 2015, 06:00 AM  #113 
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Join Date: Sep 2013

Actually its probably closer to 1.5x (sorry for any confusion)
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6th December 2015, 11:26 PM  #114 
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Join Date: Aug 2006
Location: Texas

Sorry, it was an oversight. I will post the correct models later.
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7th December 2015, 12:50 AM  #115 
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Join Date: Dec 2005
Location: Kuala Lumpur

Well spotted.
This is why simulation often gives unrealistic levels of distortion. N and P or npn and pnp complementary devices are never as close as as most simulation models assume 
7th December 2015, 01:14 AM  #116 
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Join Date: Sep 2013

That would be great.
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8th December 2015, 08:53 PM  #117 
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Join Date: Aug 2006
Location: Texas

Nowadays it's hard to get N/P copies unless you use those models or use the perfect simulator defaults, so it's actually pretty unlikely to have this problem in simulation. That said, people who make models for audio amps tend to pick matched transistors to base them on, so some of the models floating around match closer than you would expect out of the box. Still, there are a lot of other distortion mechanisms that can dominate even if the transistors are matched. In practice you want to look at more than transistor matching to lower overall distortion in an amplifier.
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8th December 2015, 10:17 PM  #118  
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Join Date: Sep 2006

Quote:
Although generalizing can be dangerous, N/P mismatch will often lead more to evenorder harmonics. Also, with BJT output stages, people often match for beta, but the degree to which an amplifier is affected by N/P beta mismatch is often a strong function of the output stage topology. For example, a simple 2EF output stage is more affected by beta mismatch than a Triple. Crossover distortion is one of the most insidious concerns, but the extent to which N/P matching reduces it is hard to predict. One can always say that matching can never hurt. N/P matching for MOSFETs is more difficult, and usually can't really be done because of the physics of the devices. Matching Vgs of the N and P devices does virtually nothing for distortion in most MOSFET output stages. Note that this is not the same as the issue of matching among likesex MOSFETs in multiple output pair stages. The more significant issue of N vs P MOSFETs is the amount of transconductance that each has at a given drain current. Many MOSFET output stages do not employ source resistors because they are really not needed for the same reason as emitter resistors are used in BJT output stages. However, it has been my experience that sometimes adding smallvalue source resistors of different values for the N and P vertical MOSFET devices can help some. I discuss this in Chapter 11 of my book. It is certainly not a perfect solution, but it can help some. Small value in this context is less than 1 ohm. Cheers, Bob 

9th December 2015, 05:45 AM  #119 
nhinstruments
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11th December 2015, 02:11 PM  #120 
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Join Date: Aug 2006
Location: Texas

Here are the corrected models and the same jig as before.
The use of the Tjp models is explained here: http://www.diyaudio.com/forums/softw...ml#post4365741 Code:
* * MOSFET VDMOS Models with ksubthres *For 25C * *10N2025 VDMOS with subthreshold (c) Ian Hegglun 06 Dec 2015 .model 10N2025 VDMOS (Rg=60 Vto={0.171.6m*0} Lambda=3m + Rs={0.245*(1+2.6m*0)} Kp={1.30/(1+8.3m*0)} + Ksubthres={0.095*(1+2.9m*0)} Mtriode=0.3 Rd={0.6*(1+3m*0)} + Cgdmax=100p Cgdmin=5p a=0.25 Cgs=600p Cjo=1100p + m=0.7 VJ=2.5 IS=4.0E6 N=2.4 mfg=IH151206) * * * *10P2025 VDMOS with subthreshold (c) Ian Hegglun 06 Dec 2015 .model 10P2025 VDMOS (pchan Rg=60 Vto={0.535+1.7m*0} + Rs={0.37*(1+3.4m*0)} Kp={0.995/(1+6.7m*0)} Rd=0.2 + Ksubthres={0.12*(1+3.1m*0)} Mtriode=0.4 Lambda=5m + Cgdmax=215p Cgdmin=10p a=0.25 Cgs=900p Cjo=1200p + m=0.7 VJ=2.5 IS=4.0E6 N=2.4 mfg=IH151206) * * * *20N2025 VDMOS with subthreshold (c) Ian Hegglun 06 Dec 2015 .model 20N2025 VDMOS (Rg=30 Vto={0.1551.6m*0} + Rs={0.12*(1+2.5m*0)} Kp={2.40/(1+7.4m*0)} + Ksubthres={0.09*(1+1m*0)} Mtriode=0.3 Rd=0.16 Lambda=3m + Cgdmax=200p Cgdmin=10p a=0.25 Cgs=1200p Cjo=2200p + m=0.7 VJ=2.5 IS=8.0E6 N=2.4 mfg=IH151206) * * * *20P2025 VDMOS with subthreshold (c) Ian Hegglun 06 Dec 2015 .model 20P2025 VDMOS (pchan Rg=30 Vto={0.61+2.2m*0} + Rs={0.17*(1+2.0m*0)} Kp={1.85/(1+8.4m*0)} + Ksubthres={0.105*(1+5m*0)} Mtriode=0.35 Rd=0.05 Lambda=5m + Cgdmax=430p Cgdmin=20p a=0.25 Cgs=1800p Cjo=2400p + m=0.7 VJ=2.5 IS=8.0E6 N=2.4 mfg=IH151206) * * ************************************************************** * For 75C * *10N2075 VDMOS with subthreshold (c) Ian Hegglun 06 Dec 2015 .model 10N2075 VDMOS (Rg=60 Vto={0.171.6m*50} Lambda=3m + Rs={0.245*(1+2.6m*50)} Kp={1.30/(1+8.3m*50)} + Ksubthres={0.095*(1+2.9m*50)} Mtriode=0.3 Rd={0.6*(1+3m*50)} + Cgdmax=100p Cgdmin=5p a=0.25 Cgs=600p Cjo=1100p + m=0.7 VJ=2.5 IS=4.0E6 N=2.4 mfg=IH151206) * * * *10P2075 VDMOS with subthreshold (c) Ian Hegglun 06 Dec 2015 .model 10P2075 VDMOS (pchan Rg=60 Vto={0.535+1.7m*50} + Rs={0.37*(1+3.4m*50)} Kp={0.995/(1+6.7m*50)} Rd=0.2 + Ksubthres={0.12*(1+3.1m*50)} Mtriode=0.4 Lambda=5m + Cgdmax=215p Cgdmin=10p a=0.25 Cgs=900p Cjo=1200p + m=0.7 VJ=2.5 IS=4.0E6 N=2.4 mfg=IH151206) * * * *20N2075 VDMOS with subthreshold (c) Ian Hegglun 06 Dec 2015 .model 20N2075 VDMOS (Rg=30 Vto={0.1551.6m*50} + Rs={0.12*(1+2.5m*50)} Kp={2.40/(1+7.4m*50)} + Ksubthres={0.09*(1+1m*50)} Mtriode=0.3 Rd=0.16 Lambda=3m + Cgdmax=200p Cgdmin=10p a=0.25 Cgs=1200p Cjo=2200p + m=0.7 VJ=2.5 IS=8.0E6 N=2.4 mfg=IH151206) * * * *20P2075 VDMOS with subthreshold (c) Ian Hegglun 06 Dec 2015 .model 20P2075 VDMOS (pchan Rg=30 Vto={0.61+2.2m*50} + Rs={0.17*(1+2.0m*50)} Kp={1.85/(1+8.4m*50)} + Ksubthres={0.105*(1+5m*50)} Mtriode=0.35 Rd=0.05 Lambda=5m + Cgdmax=430p Cgdmin=20p a=0.25 Cgs=1800p Cjo=2400p + m=0.7 VJ=2.5 IS=8.0E6 N=2.4 mfg=IH151206) * * ******************************************************** * MOSFET VDMOSTjp Models with ksubthres * * *10N20Tjp VDMOS with subthreshold (c) Ian Hegglun 06 Dec 2015 .model 10N20Tjp VDMOS (Rg=60 Vto={0.171.6m*(Tjp25)} Lambda=3m + Rs={0.245*(1+2.6m*(Tjp25))} Kp={1.30/(1+8.3m*(Tjp25))} + Ksubthres={0.095*(1+2.9m*(Tjp25))} Mtriode=0.3 Rd={0.6*(1+3m*(Tjp25))} + Cgdmax=100p Cgdmin=5p a=0.25 Cgs=600p Cjo=1100p + m=0.7 VJ=2.5 IS=4.0E6 N=2.4 mfg=IH151206) * * * *10P20Tjp VDMOS with subthreshold (c) Ian Hegglun 06 Dec 2015 .model 10P20Tjp VDMOS (pchan Rg=60 Vto={0.535+1.7m*(Tjp25)} + Rs={0.37*(1+3.4m*(Tjp25))} Kp={0.995/(1+6.7m*(Tjp25))} Rd=0.2 + Ksubthres={0.12*(1+3.1m*(Tjp25))} Mtriode=0.4 Lambda=5m + Cgdmax=215p Cgdmin=10p a=0.25 Cgs=900p Cjo=1200p + m=0.7 VJ=2.5 IS=4.0E6 N=2.4 mfg=IH151206) * * * *20N20Tjp VDMOS with subthreshold (c) Ian Hegglun 06 Dec 2015 .model 20N20Tjp VDMOS (Rg=30 Vto={0.1551.6m*(Tjp25)} + Rs={0.12*(1+2.5m*(Tjp25))} Kp={2.40/(1+7.4m*(Tjp25))} + Ksubthres={0.09*(1+1m*(Tjp25))} Mtriode=0.3 Rd=0.16 Lambda=3m + Cgdmax=200p Cgdmin=10p a=0.25 Cgs=1200p Cjo=2200p + m=0.7 VJ=2.5 IS=8.0E6 N=2.4 mfg=IH151206) * * * *20P20Tjp VDMOS with subthreshold (c) Ian Hegglun 06 Dec 2015 .model 20P20Tjp VDMOS (pchan Rg=30 Vto={0.61+2.2m*(Tjp25)} + Rs={0.17*(1+2.0m*(Tjp25))} Kp={1.85/(1+8.4m*(Tjp25))} + Ksubthres={0.105*(1+5m*(Tjp25))} Mtriode=0.35 Rd=0.05 Lambda=5m + Cgdmax=430p Cgdmin=20p a=0.25 Cgs=1800p Cjo=2400p + m=0.7 VJ=2.5 IS=8.0E6 N=2.4 mfg=IH151206) * * **************************************************************
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The Kmultiplier rail filter! = The Simple Kuartlotron Superbuffer! Need something built, repaired or modded? PM me and ask what I can do! Last edited by keantoken; 11th December 2015 at 02:19 PM. 
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