Is there something wrong with PMOS model in the LTSpice XVII?

You're evading my point. I said it is possible to write a proper model. It just hasn't been done (properly) yet, though I've developed a model that's pretty close, it's not _perfect_... I strive for perfection so I'm still playing with it as time permits ;-)

Yes. Pretty much as long as you can write an equation for it Spice can solve it. ...Jim Thompson

I'm not evading your point, I'm disagreeing with it. I claim that no such model exists, and you appear to agree. Your faith in SPICE is touching but provably wrong--it can't model everything without hacking the simulator code, not merely the models.

For something whose behaviour is fairly simple and which has wide device-to-device variations, such as a diode with diffusion overshoot, you can probably cruft together some subcircuit model that gets vaguely into the ballpark, maybe using the transmission line model to account for time delays.

It sure won't be just D() with parameters, though.

No. Not transport equations, as I said, and there are lots of other examples of integral or integrodifferential equations. They're generally not reducible to systems of ODEs, because no ODE can be nonlocal, and so no solver limited to ODEs can handle them.

You can't even write an ODE to describe a piece of coax from a circuits point of view--the SPICE transmission line isn't an ODE model, it's a special case, i.e. the simulator code has to be hacked up to support it.

Cheers

Phil Hobbs

That's the datasheet. I'd expect a "real" Spice model (as opposed to an LTspice-hokeyed model) to properly simulate the enhanced operation.

I just tried an Infineon BSP135_L0, and it does, though it looks like the model doesn't model the knee very well at all... LEVEL=3 model... in the real world we're up to model LEVEL's in the 50's ;-) ...Jim Thompson

Baloney. There's where subcircuits come in.

Transmission line models are a disaster.

Nope. I never said it would.

Watch this space ;-) ...Jim Thompson

Yikes.

Since Schottkys have gotten so cheap, I just use them when forward recovery might be an issue, so I don't have to care about the stupidity of SPICE diodes. Back in the day when they were $2, it was a harder call.

Agreed. Simulation is not an adequate substitute for thought, though it's often used that way.

Cheers

Phil Hobbs

Where I was back in August when I last toyed with it...

...Jim Thompson

I use BAT54s for medium power things, like everyone else. The sampler I recently did used one DB2S31400L (30V, 30mA, 3pF, $0.02) to control the gate of the S/H JFET, and one 1PS10SB82 (15V, 30mA, 1pF, $0.16) for the actual sampler. Worked fine.

Until you get to reach-through, where the bottom of the potential well flattens out at the electrode potential.

Interdigitated Schottky photodiodes have back-to-back barriers, so you have to bias them above reachthrough before they conduct at all. Some APDs are like that--they don't work at zero bias.

Cheers

Phil Hobbs

My commodity part is SMS7621/BAT15 in SOD323. It has around 0.25 pF capacitance. They are safe up to at least 6 volts. We average about 20 cents each.

Schottkies don't avalanche or anything dramatic; they just leak more as reverse voltage goes up.

If something like forward recovery looks to be a problem, use a different part!

A good SRD model could be handy, but that can be finessed with a charge-controlled switch or something. But I wouldn't trust a sim that uses an SRD; that's breadboard territory.

A boy needs to solder now and then anyhow.

I still have a couple of pounds of 60/40 on hand, plus a Weller WES51 station. ...Jim Thompson

-- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

Thinking outside the box... producing elegant solutions.

For exotica like phemts, it's easier, and far more believable, to breadboard a circuit, rather than spending gobs of time fiddling with a Spice model of unknown accuracy.

I don't often need a full, accurate Spice model. If I'm switching a phemt on or off, I just need to make a few DC measurements.

The RF boys can live with the s-params, as long as they can figure out how to get the drain current right. Some of the data sheets say "adjust the gate voltage for xxx mA drain current [best of luck] "

I guess that designing monolithic ICs discourages breadboarding. Nobody makes Dremels tiny enough.

They do, actually--focused ion beam (FIB) tools. You can dig nice straight sided trenches, and put down platinum wires too.

I've only driven one once, but it was pretty cool.

You should talk your way into a tour of somebody's Failure Analysis lab--good ones have an amazing array of fun tools like that.

Cheers

Phil Hobbs

I started using a simulator somewhere around 1977-1980 (Berkeley Spice on a VAX780), but I continued to do bread-boarding until ~1990.

There used to be packages of bipolar IC devices, called "kit-parts" (*). See "BreadBoard.jpg" on the S.E.D/Schematics Page of my website for an example. I created that board while I was Analog Guru at OmniComp/GenRad. I still have pieces of it that I use for G-jobs... original size was 1' x 1' with 72 (IIRC) up to 16 pin DIL socket locations.

(*) 4-5 devices per package, different packages for different sizes (emitter-size scale factor) ...Jim Thompson

I've never had to use that for repairs, but I've used it for a quicky test of a re-wire scheme to change a chip function, before going to the expense of a wafer run.

...Jim Thompson

On Fri, 20 Jan 2017 16:39:04 +0200, LM wrote:

First, thank you for interesting discussion accuracy. I wonder how do climate scientist test their simulations. By waiting a couple of thousand years, I quess.

I have now bought a Pfet and 200uH coil. I couldn't find such fet here. It is IRF5305, if somebody is interested. I chose low gate capacitance and availability.

The latest circuit seems to work well in simulations, It doesn't require elyt cap, which is good for reliability. I canged a couple of parts, like the main diode.

If I yield a bit, what do you think using a comparator and a smittrigger oscillator. Like this. Even LTspice rejects it so it is not ready, but the idea is there.

Version 4 SHEET 1 1032 680 WIRE 48 -272 -16 -272 WIRE 208 -272 48 -272 WIRE 288 -272 208 -272 WIRE 352 -272 288 -272 WIRE 624 -272 352 -272 WIRE -16 -256 -16 -272 WIRE -16 -160 -16 -176 WIRE 48 -64 48 -272 WIRE 144 -32 128 -32 WIRE 256 -32 224 -32 WIRE 352 -32 352 -272 WIRE 624 0 624 -272 WIRE 256 16 256 -32 WIRE 304 16 256 16 WIRE 512 16 416 16 WIRE 576 16 512 16 WIRE 128 64 128 -32 WIRE 128 64 96 64 WIRE 160 64 128 64 WIRE 256 64 256 16 WIRE 256 64 224 64 WIRE 96 96 96 64 WIRE 192 96 96 96 WIRE 96 112 96 96 WIRE 352 128 352 64 WIRE 592 144 528 144 WIRE 624 144 624 96 WIRE 624 144 592 144 WIRE 48 224 48 16 WIRE 432 224 48 224 WIRE 528 224 528 144 WIRE 528 224 432 224 WIRE 608 224 528 224 WIRE 768 224 688 224 WIRE 816 224 768 224 WIRE 864 224 816 224 WIRE 864 240 864 224 WIRE 288 288 288 -272 WIRE 496 304 320 304 WIRE 192 320 192 96 WIRE 256 320 192 320 WIRE 768 320 768 224 WIRE 864 320 864 304 WIRE 144 336 144 320 WIRE 352 336 320 336 WIRE 496 336 496 304 WIRE 432 352 432 224 WIRE 864 400 864 384 WIRE 864 400 640 400 WIRE 96 448 96 176 WIRE 288 448 288 352 WIRE 288 448 96 448 WIRE 432 448 432 416 WIRE 432 448 288 448 WIRE 496 448 496 416 WIRE 496 448 432 448 WIRE 768 448 768 384 WIRE 768 448 496 448 WIRE 784 448 768 448 WIRE 864 448 864 400 WIRE 432 480 432 448 WIRE 352 528 352 336 WIRE 640 528 640 400 WIRE 640 528 352 528 FLAG 432 480 0 FLAG -16 -160 0 FLAG 512 16 M1G FLAG 592 144 M1D FLAG 816 224 Vout FLAG 208 -272 Vcc FLAG 352 128 0 SYMBOL voltage -16 -272 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value 12 SYMBOL ind 704 208 R90 WINDOW 0 5 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName L1

SYMBOL schottky 448 416 R180 WINDOW 0 24 64 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D1 SYMATTR Value MBRS1100 SYMATTR Description Diode SYMATTR Type diode SYMBOL LED 848 240 R0 SYMATTR InstName D2 SYMATTR Value XlampMX6 SYMATTR Description Diode SYMATTR Type diode SYMBOL LED 848 320 R0 SYMATTR InstName D3 SYMATTR Value LXHL-BW02 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 32 -80 R0 SYMATTR InstName R4 SYMATTR Value 10k SYMBOL cap 752 320 R0 SYMATTR InstName C1

SYMBOL pmos 576 96 M180 SYMATTR InstName M1 SYMATTR Value RRS090P03 SYMBOL Digital\\schmtinv 160 0 R0 SYMATTR InstName A1 SYMBOL res 128 -16 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 0 56 VBottom 2 SYMATTR InstName R5 SYMATTR Value 10k SYMBOL cap 80 112 R0 SYMATTR InstName C2 SYMATTR Value 10n SYMBOL Comparators\\LM339 288 384 R180 SYMATTR InstName U1 SYMBOL voltage 496 320 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V2 SYMATTR Value 0.3 SYMBOL res 768 464 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 0 56 VBottom 2 SYMATTR InstName R1 SYMATTR Value 1 SYMBOL Digital\\inverter_philips 352 -48 R0 SYMATTR InstName U2 TEXT 320 -336 Left 2 !.tran 0 5m 0 10u startup TEXT 320 -360 Left 2 ;'Buck LED Driver NXP AN10739

Full Schematic at...

Message-ID:

It comes up as missing symbols for...

LM339 inverter_philips

So please post the appropriate .asy symbols ...Jim Thompson

Phil, Comments about my link?

Ain't no transmission line in my model.

Ain't no hack of simulator code.

Just using conventional subcircuit techniques.

And NO inductors.

Only thing holding me back from releasing it is that it requires tweak-test-tweak-test... to fit the data, and I'm looking for ways to easily parameterize it.

Got to think outside the box >:-} ...Jim Thompson

inverter_philips.asy The + and - suplplies of the comparator may be swapped in the file I sent.

Version 4 SymbolType CELL LINE Normal -16 80 -16 48 LINE Normal 64 64 32 64 LINE Normal -16 80 16 64 LINE Normal -16 48 16 64 LINE Normal -16 64 -48 64 LINE Normal 0 56 0 16 LINE Normal 0 72 0 112 RECTANGLE Normal 48 96 -32 32 CIRCLE Normal 32 72 16 56 WINDOW 0 16 16 Left 0 WINDOW 3 16 112 Left 0 SYMATTR Value INVERT SYMATTR Description Inverter gate SYMATTR Prefix X PIN -48 64 NONE 8 PINATTR PinName A PINATTR SpiceOrder 1 PIN 64 64 NONE 0 PINATTR PinName Y PINATTR SpiceOrder 2 PIN 0 16 NONE 8 PINATTR PinName VCC PINATTR SpiceOrder 3 PIN 0 112 NONE 8 PINATTR PinName VSS PINATTR SpiceOrder 4

lm339.asy

Version 4 SymbolType CELL LINE Normal -32 32 32 64 LINE Normal -32 96 32 64 LINE Normal -32 32 -32 96 LINE Normal -28 48 -20 48 LINE Normal -28 80 -20 80 LINE Normal -24 84 -24 76 LINE Normal 0 32 0 48 LINE Normal 0 96 0 80 LINE Normal 4 44 12 44 LINE Normal 8 40 8 48 LINE Normal 4 84 12 84 WINDOW 0 16 32 Left 0 WINDOW 3 16 96 Left 0 SYMATTR Value LM339 SYMATTR Prefix X SYMATTR SpiceModel LM339.sub SYMATTR Value2 LM339 SYMATTR Description Quad Single Supply 3V/5V Comparator LM339 PIN -32 80 NONE 0 PINATTR PinName In+ PINATTR SpiceOrder 1 PIN -32 48 NONE 0 PINATTR PinName In- PINATTR SpiceOrder 2 PIN 0 32 NONE 0 PINATTR PinName V+ PINATTR SpiceOrder 3 PIN 0 96 NONE 0 PINATTR PinName V- PINATTR SpiceOrder 4 PIN 32 64 NONE 0 PINATTR PinName OUT PINATTR SpiceOrder 5

LM339.sub

• LM339 VOLTAGE COMPARATOR "MACROMODEL" SUBCIRCUIT

• CREATED USING PARTS VERSION 4.03 ON 03/07/90 AT 14:17

• REV (N/A)

• CONNECTIONS: NON-INVERTING INPUT

• | INVERTING INPUT

• | | POSITIVE POWER SUPPLY

• | | | NEGATIVE POWER SUPPLY

• | | | | OPEN COLLECTOR OUTPUT

• | | | | | .SUBCKT LM339 1 2 3 4 5

• F1 9 3 V1 1 IEE 3 7 DC 100.0E-6 VI1 21 1 DC .75 VI2 22 2 DC .75 Q1 9 21 7 QIN Q2 8 22 7 QIN Q3 9 8 4 QMO Q4 8 8 4 QMI .MODEL QIN PNP(IS=800.0E-18 BF=2.000E3) .MODEL QMI NPN(IS=800.0E-18 BF=1002) .MODEL QMO NPN(IS=800.0E-18 BF=1000 CJC=1E-15 TR=807.4E-9) E1 10 4 9 4 1 V1 10 11 DC 0 Q5 5 11 4 QOC .MODEL QOC NPN(IS=800.0E-18 BF=20.29E3 CJC=1E-15 TF=942.6E-12 TR=543.8E-9) DP 4 3 DX RP 3 4 46.3E3 .MODEL DX D(IS=800.0E-18)

• .ENDS

• Model for packaged LM339 devices

• 14-pin DIP, 4 comparators per package

• CONNECTIONS: Output 2

• | Output 1

• | | Positive Power Supply

• | | | Input 1 Inverting

• | | | | Input 1 Non-Inverting

• | | | | | Input 2 Inverting

• | | | | | | Input 2 Non-Inverting

• | | | | | | | Input 3 Inverting

• | | | | | | | | Input 3 Non-inverting

• | | | | | | | | | Input 4 Inverting

• | | | | | | | | | | Input 4 Non-inverting

• | | | | | | | | | | | Negative Power Supply (or Gnd)

• | | | | | | | | | | | | Output 4

• | | | | | | | | | | | | | Output 3

• | | | | | | | | | | | | | | .SUBCKT LM339_DIP14 1 2 3 4 5 6 7 8 9 10 11 12 13 14 X1 5 4 3 12 2 LM339 X2 7 6 3 12 1 LM339 X3 9 8 3 12 14 LM339 X4 11 10 3 12 13 LM339 .ENDS

If I build this, I will use 4093 as the oscillator and inverter. Some open collector comparator like LM339. But where to measure the current. I am not sure about doing it like I did it now.