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Guest

Mon Jan 06, 2020 3:03 am   



Do you have a Spice model for SAV551 or something similar?



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Phil Hobbs
Guest

Mon Jan 06, 2020 3:51 am   



On 2020-01-05 20:03, jlarkin_at_highlandsniptechnology.com wrote:
> Do you have a Spice model for SAV551 or something similar?

I don't have any E-pHEMT models, and LTspice doesn't understand the
Avago datasheet models.

I've used this one in the past:

* Depletion pHEMT

* This is the datasheet model, except that LTspice doesn't understand a
bunch of
* the parameters given by Avago--we'll see if it works

..MODEL ATF38143_chip NMF( vto=-0.75, Beta=0.3, Lambda=0.07, Alpha=4,
+ B=0.8, Pb=0.7, Cgs=0.997E-12,
+ Cgd=0.176E-12, Rd=0.084, Rs=0.054, Kf=1e6, Af=1)

There are also these:
<http://www.hp.woodshot.com/hprfhelp/products/xrs/atf34xxx.htm>

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com


Guest

Mon Jan 06, 2020 5:23 am   



On Sun, 5 Jan 2020 20:51:15 -0500, Phil Hobbs
<pcdhSpamMeSenseless_at_electrooptical.net> wrote:

Quote:
.MODEL ATF38143_chip NMF( vto=-0.75, Beta=0.3, Lambda=0.07, Alpha=4,
+ B=0.8, Pb=0.7, Cgs=0.997E-12,
+ Cgd=0.176E-12, Rd=0.084, Rs=0.054, Kf=1e6, Af=1)


Cool. Thanks. It works as a depletion mesfet. I can tweak that to make
it work more like a SAV541. Might add some drain inductance maybe. I
will use the 541 as a switch to discharge the cap in a linear ramp
generator, so the model can be a little crude; it's not likely to
oscillate!


Version 4
SHEET 1 880 680
WIRE 288 -96 64 -96
WIRE 64 -32 64 -96
WIRE 64 96 64 48
WIRE 128 96 64 96
WIRE 176 96 128 96
WIRE 64 160 64 96
WIRE 288 160 288 -96
WIRE -64 240 -128 240
WIRE 16 240 -64 240
WIRE -128 272 -128 240
WIRE 64 304 64 256
WIRE 288 304 288 240
WIRE -128 384 -128 352
FLAG 64 304 0
FLAG 288 304 0
FLAG -128 384 0
FLAG -64 240 G
FLAG 128 96 D
SYMBOL mesfet 16 160 R0
WINDOW 0 100 31 Left 2
WINDOW 3 89 65 Left 2
SYMATTR InstName Z1
SYMATTR Value SAV
SYMBOL voltage 288 144 R0
WINDOW 0 55 47 Left 2
WINDOW 3 63 77 Left 2
SYMATTR InstName V1
SYMATTR Value 5
SYMBOL res 48 -48 R0
WINDOW 0 -72 45 Left 2
WINDOW 3 -74 84 Left 2
SYMATTR InstName R1
SYMATTR Value 100
SYMBOL voltage -128 256 M0
WINDOW 0 62 58 Left 2
WINDOW 3 51 96 Left 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value SINE(-0.5 1 1)
TEXT -160 464 Left 2 !.MODEL SAV NMF( vto=-0.75, Beta=0.3,
Lambda=0.07, Alpha=4,\n+ B=0.8, Pb=0.7,
Cgs=0.997E-12,\n+ Cgd=0.176E-12, Rd=0.084,
Rs=0.054, Kf=1e6, Af=1)
TEXT 128 392 Left 2 !.tran 5
TEXT 376 320 Left 2 ;First cut at SAV541 model
TEXT 376 360 Left 2 ;using Phil's mesfet model
TEXT 432 408 Left 2 ;JL Jan 5 2020



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Phil Hobbs
Guest

Mon Jan 06, 2020 8:02 pm   



On 2020-01-05 22:23, jlarkin_at_highlandsniptechnology.com wrote:
Quote:
On Sun, 5 Jan 2020 20:51:15 -0500, Phil Hobbs
pcdhSpamMeSenseless_at_electrooptical.net> wrote:

.MODEL ATF38143_chip NMF( vto=-0.75, Beta=0.3, Lambda=0.07, Alpha=4,
+ B=0.8, Pb=0.7, Cgs=0.997E-12,
+ Cgd=0.176E-12, Rd=0.084, Rs=0.054, Kf=1e6, Af=1)


Cool. Thanks. It works as a depletion mesfet. I can tweak that to make
it work more like a SAV541. Might add some drain inductance maybe. I
will use the 541 as a switch to discharge the cap in a linear ramp
generator, so the model can be a little crude; it's not likely to
oscillate!


The other link I posted has the package parasitics, which are probably
pretty similar.

Just for fun I instrumented your circuit and found that VAF is right
around 14 volts for this model. I think that might be a bit optimistic
for the Avago part.

<https://electrooptical.net/www/sed/JLphemtVAF.png>
<https://electrooptical.net/www/sed/JLphemtVAF.asc>
<https://electrooptical.net/www/sed/JLphemtVAF.plt>

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

David Nadlinger
Guest

Wed Jan 08, 2020 3:41 pm   



On 06.01.20 1:03 am, jlarkin_at_highlandsniptechnology.com wrote:
> Do you have a Spice model for SAV551 or something similar?

I don't, at least not for LTspice, but would be interested in one. The
obvious choice would be to use the ATF-55134 model from the
Agilent/Avago datasheet and hope it's close enough:
https://media.digikey.com/pdf/Data%20Sheets/Avago%20PDFs/ATF-55143.pdf
(page 16)

Unfortunately, that happens to use the ADS-flavoured quadratic Curtice
model, though, which other SPICEs don't implement. You could try and use
this as a basis for further fiddling:

..MODEL SAV551 NMF(Vto=0.3, Beta=0.444, B=0.8, Alpha=13, Lambda=0.072,
Rd=2.025, Rs=0.675, Cgs=0.6193E-12, Cgd=0.1435E-12, Pb=0.7, Fc=0.65)

This is a mechanical translation of the coefficients from the datasheet,
which might or might not give sensible results. You'd need to tune the B
value to match your measurements… Package parasitics could be included
in a SUBCKT as per the ATF-55143 datasheet.

Another option might be to just fit the model parameters to the data I
recall you posting elsewhere. The data for MCL's I_DS/V_DS curves is
available as well:
https://www.minicircuits.com/pages/s-params/SAV-551+_VIEW.pdf. You could
use their S parameters to get the parasitic reactances, and maybe
extract some more graphs to fit from an ADS sim if you have access to a
license. Never tried this, though, so caveat emptor.

On another note, does anyone know how NMF is supposed to work for noise
simulations in LTspice? The results seem wildly off (too large by orders
of magnitude), but I can't find any reference as to which model it is
even supposed to use (McWhorther 1/f noise plus broadband noise inferred
from transconductance?).

— David


Guest

Wed Jan 08, 2020 5:19 pm   



On Wed, 8 Jan 2020 13:41:40 +0000, David Nadlinger
<david_at_klickverbot.at> wrote:

Quote:
On 06.01.20 1:03 am, jlarkin_at_highlandsniptechnology.com wrote:
Do you have a Spice model for SAV551 or something similar?

I don't, at least not for LTspice, but would be interested in one. The
obvious choice would be to use the ATF-55134 model from the
Agilent/Avago datasheet and hope it's close enough:
https://media.digikey.com/pdf/Data%20Sheets/Avago%20PDFs/ATF-55143.pdf
(page 16)

Unfortunately, that happens to use the ADS-flavoured quadratic Curtice
model, though, which other SPICEs don't implement. You could try and use
this as a basis for further fiddling:

.MODEL SAV551 NMF(Vto=0.3, Beta=0.444, B=0.8, Alpha=13, Lambda=0.072,
Rd=2.025, Rs=0.675, Cgs=0.6193E-12, Cgd=0.1435E-12, Pb=0.7, Fc=0.65)

This is a mechanical translation of the coefficients from the datasheet,
which might or might not give sensible results. You'd need to tune the B
value to match your measurements… Package parasitics could be included
in a SUBCKT as per the ATF-55143 datasheet.

Another option might be to just fit the model parameters to the data I
recall you posting elsewhere. The data for MCL's I_DS/V_DS curves is
available as well:
https://www.minicircuits.com/pages/s-params/SAV-551+_VIEW.pdf. You could
use their S parameters to get the parasitic reactances, and maybe
extract some more graphs to fit from an ADS sim if you have access to a
license. Never tried this, though, so caveat emptor.

On another note, does anyone know how NMF is supposed to work for noise
simulations in LTspice? The results seem wildly off (too large by orders
of magnitude), but I can't find any reference as to which model it is
even supposed to use (McWhorther 1/f noise plus broadband noise inferred
from transconductance?).

— David


Thanks, I'll plug that in and see how it compares to a real part.

I'm using the SAV541 to discharge a linear-ramp capacitor, so the only
parasitic of great concern is drain inductance. I can measure that
with TDR and add it to my circuit as a discrete inductor.

The trick with grounded-cap ramps is to keep the early part clean,
linear and not ringing. The faster the discharge switch, the more it
all wants to ring.



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

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