2N7000 Spice Model

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Last time I tested several 2N7000 Spice models (2005), there was huge
variance between them, and some down-right non-physical behavior.

Has anyone found a better 2N7000 model since then?
        
                                        ...Jim Thompson
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| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
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Re: 2N7000 Spice Model
On Tue, 17 Jun 2014 09:38:18 -0700, Jim Thompson

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The 2N7000/2N7002 parts themselves vary a lot between manufacturers,
which is why some of our products specify a specific manufacturer for
these parts.

What non-physical behavior are you seeing?




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John Larkin         Highland Technology, Inc

jlarkin att highlandtechnology dott com
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Re: 2N7000 Spice Model
On 17/06/2014 20:02, John Larkin wrote:
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I would hope to see some electrical behaviour!

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Mike Perkins
Video Solutions Ltd
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Re: 2N7000 Spice Model
On Tue, 17 Jun 2014 12:02:40 -0700, John Larkin

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All but the Supertex model failed to model ANY behavior below
threshold, and the Supertex model had discontinuities in the ID/VDS
curve blending... guaranteed to cause simulator convergence issues.
        
                                        ...Jim Thompson
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Re: 2N7000 Spice Model
On Tue, 17 Jun 2014 14:15:32 -0700, Jim Thompson

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I forgot to reference my old post (4/6/2005)...

http://www.analog-innovations.com/SED/Compare2N7000Models.pdf

Second page tells it all.
        
                                        ...Jim Thompson
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Re: 2N7000 Spice Model
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Jim Thompson wrote:
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   Fairchild FQD2N100 model attached.


--------------070406050500050804060902
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*******************************************************************************
*  You can read about the added-diode-approach in Steven M. Sandler's
*  article in Power Electronics Technology, May 2005.
*******************************************************************************

*                D  G  S        Original model
.SUBCKT FQD2N100  d  g  s
Rg  g 1 0.04
M1 2 1 3 3 DMOS L=1u W=1u
.MODEL DMOS NMOS(VTO=4.66  KP=1.9  LEVEL=3)
Cgs 1 3 380p
Rd  d 4 3.5
Dds 3 4 DDS
.MODEL DDS D(BV10%50  M=0.42  CJO35%p  VJ=0.12)
Dbody 3  d DBODY
.MODEL DBODY D(IS=2.8E-13  N=1.00  RS=0.005  EG=1.10  TT52%0n)
Ra 4 2 3.5
Rs 3 5 0.024
Ls 5  s 2.6n
M2 1 8 6 6 INTER
E2 8 6 4 1 2
.MODEL INTER NMOS(VTO=0  KP10%  LEVEL=1)
CGDMAX 7 4 380p
RCGD 7 4 1E7
DGD 6 4 DGD
RDGD 4 6 1E7
.MODEL DGD D(M=0.52  CJO38%0p  VJ=0.12)
M3 7 9 1 1 INTER
E3 9 1 4 1 -2
.ENDS

* And here's my modified model (assuming I found the right file).
* Leakage current corrected by raising RDGD to 1G-ohm.
*                  D  G  S
.SUBCKT FQD2N100xG  d  g  s
* see Motorola an1043 fig 2 for Cdg model
Rg  g 1 0.04
Dg 1 11 Dsubthres
.MODEL Dsubthres D (N=5.5 IS=0.1n  EG=1.1)
F1 11 1 VSNS 1
M1 2 11 3 3 DMOS L=1u W=1u
.MODEL DMOS NMOS(VTO=2.0  KP=1.9  LEVEL=3)
Cgs 1 3 1p
Rd  d 4 3.5
Dds 15 4 DDS
.MODEL DDS D(BV10%50  M=0.42  CJO35%p  VJ=0.12)
Dbody 15  d DBODY
.MODEL DBODY D(IS=2.8E-13  N=1.00  RS=0.005  EG=1.10  TT52%0n)
Ra 4 2 3.5
VSNS 3 15
Ciss 1 15 380p
Rs 15 5 0.024
Ls 5  s 2.6n
M2 1 8 6 6 INTER
E2 8 6 4 1 2
.MODEL INTER NMOS(VTO=0  KP10%  LEVEL=1)
CGDMAX 7 4 380p
RCGD 7 4 1E9
DGD 6 4 DGD
RDGD 4 6 1E9
.MODEL DGD D(M=0.52  CJO38%0p  VJ=0.12)
M3 7 9 1 1 INTER
E3 9 1 4 1 -2
.ENDS


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Re: 2N7000 Spice Model
On Tue, 17 Jun 2014 14:23:41 -0700, Jim Thompson

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If you're actually designing boards with 2N7000s, any of those curves is about
as good as any other. Real-life parts will be all over the map.


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John Larkin                  Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

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Re: 2N7000 Spice Model
On Tue, 17 Jun 2014 19:44:42 -0700, John Larkin

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You didn't notice the discontinuities?
        
                                        ...Jim Thompson
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Re: 2N7000 Spice Model
On Tue, 17 Jun 2014 21:35:21 -0700, Jim Thompson

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Sure, but they are down in the "noise" of part-part differences.


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John Larkin                  Highland Technology Inc
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Re: 2N7000 Spice Model
On Tue, 17 Jun 2014 21:57:08 -0700, John Larkin

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Refer back in the history of this group, and Win Hill's concern about
operation in the subthreshold region.  Use as a low noise amplifier is
quite different from just using the device as a switch.
        
                                        ...Jim Thompson
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Re: 2N7000 Spice Model
On Wed, 18 Jun 2014 07:40:52 -0700, Jim Thompson

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Here's a graph that I found in our PDATA folder for the 2N7000. I don't know
where it came from, possibly from Win.

https://dl.dropboxusercontent.com/u/53724080/Parts/Fets/2n7000_off_leakage.pdf

(people should sign and date everything that they create)

What does "subthreshold" mean anyhow? It seeme to me that specified gate
thresholds are based on arbitrary drain currents. That curve above has no
threshold.




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John Larkin                  Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

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Re: 2N7000 Spice Model
On Wed, 18 Jun 2014 07:50:07 -0700, John Larkin

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That's not "leakage", it's the natural square-law behavior of MOS
devices below "threshold"... sometimes used to make faux bandgaps with
MOS ;-)

I suspect Joerg regularly works down in this region.

I recently participated in the design of a medical device (chip) where
_everything_ operated subthreshold... the oscillators I mentioned
before... 1kHz at 6nA, 1MHz at 1.2uA

The definition of "threshold" is a vague.  I have these papers that I
can share, if any are interested...

...\ModelingIssues\ThresholdModeling_SalcedoEtAl.pdf

...\MOS-GateCharge\WinHill_subthreshold_mosfet_model.pdf (graphs)

...\MOS-GateCharge\Win Hill Datan7000_data_graphs.xls (data)

...\SubthresholdEffects\CurrentMirror_Novel_SubthresholdRegion.pdf

...\SubthresholdEffects\ExploitingSubthresholdMOSFET_Behavior.pdf

...\SubthresholdEffects\ReferencesFromSubthreshold MOSFETs.pdf

...\SubthresholdEffects\SubthresholdDeviceModeling.pdf

...\SubthresholdEffects\SubthresholdMOSforUltra-LowPower.pdf
        
                                        ...Jim Thompson
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Re: 2N7000 Spice Model
On 06/18/2014 10:50 AM, John Larkin wrote:
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Very pretty.  What was V_GS?

Cheers

Phil Hobbs


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Dr Philip C D Hobbs
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Re: 2N7000 Spice Model
On Wed, 18 Jun 2014 12:40:26 -0400, Phil Hobbs

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Do you mean Vds? I don't know.  


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John Larkin         Highland Technology, Inc

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Re: 2N7000 Spice Model
On 6/18/2014 5:06 PM, John Larkin wrote:
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V_DS, right.  Ah, well, I'll have to quit snuggling with my computer and  
actually do some measurements. ;)

Cheers

Phil Hobbs


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Dr Philip C D Hobbs
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Re: 2N7000 Spice Model
On Tue, 17 Jun 2014 19:44:42 -0700, John Larkin wrote:

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Not if the board function depends on sub-threshold behavior!

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Tim Wescott
Wescott Design Services
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Re: 2N7000 Spice Model
On Tue, 17 Jun 2014 18:21:48 -0700, Robert Baer

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No model level higher then Level=3... that is, early school-boy
text-book complexity.

The problem is that it is quite rare to see discrete MOS devices
modeled properly as BSIM3v3.
        
                                        ...Jim Thompson
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