LT Spice noise analysis

And I have foundry models... this latest job is UMC, 150nm ;-) ...Jim Thompson

You can do 150 nm litho with a crayon.

Cheers

Phil Hobbs

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Thinking outside the box... producing elegant solutions.

Last process I worked on was 22nm, and that makes me a grandpa. ;)

My nanoantennas were made on a 30-nm Leica e-beam writer, and that was getting on for a decade ago now.

Cheers

Phil Hobbs

Actually, I really like the Cadence schematic capture. LTSpice is not even in the same universe :-)

Yeah, it is a real problem without good foundry models.

I have collected quite a few sets now for all the processes I have used in my day job. Not something I can pass out with SS though.

-- Kevin Aylward

That's not so. You need rubylith and x-acto knives at 150 nm.

Small feature size is useless for precision Analog... VOS =

I'll have to check the version number tomorrow, but not nearly as bad as what I had to use 2 years ago.

Same here. I have literally libraries for at least 60 process variations.

...Jim Thompson

Dimensions are mv/um ;-) ...Jim Thompson

Transistors stopped getting better at about the 65 nm node. Now the game i s to use more transistors to counteract the dopant atom statistics (which i s probably what makes Vos hard to control). At 7nm, even logic levels aren' t that easy to control.

;)

Cheers

Phil Hobbs

Exactly. Also, 1/f noise does the same.

Currently using 0u18 process and I rarely use less than about 1u gate length for the analog bits. Typically, I use 0.18u for things like the output device of an LDO, where it don't matter, and you want it to be small as possible.

-- Kevin Aylward

I did notice something a bit strange with the LT user licence. It only prohibits use by "...semiconductor manufactures..." .

This seems a bit of a cockup on their part. Surely one would expect that they would prohibit fabless semiconductor companies or individuals using it to design competing chips, much as what you are now at liberty to do :-)

-- Kevin Aylward

Legal disclaimer... personal opinion follows...

LT management must have their heads up their ass... more and more of their models will run ONLY on LTspice, some because of encryption, some because of proprietary functions not found in any other Spice variant.

I guess they figure to sell only to amateurs ?>:-} ...Jim Thompson

Legal disclaimer... personal opinion follows...

Agreed.

-- Kevin Aylward

Am 03.03.2017 um 21:28 schrieb Kevin Aylward:

As much as I like LTspice, and I use it a lot, methinks in the long run we do ourselves a disservice with it.

Everybody attaches a small rucksack to the original Spice, renames it somewhat and then sleeps on it like the dragon on his pile of gold. And no one but LT makes any impact in user land, no one gets rich, and no one can collect the good ideas and can concentrate them in one open version so the next bright guy can build upon that.

LTspice leeches the blood out of any other development.

Maybe I should move on to NGspice or Xspice or QUCS, as an investment into the future.

There is enough to do: s-parameters, large signal noise analysis, contemporary transistor models, electromagnetics, strip lines, harmonic balance, functional blocks, using CUDA etc. There is so much that AWR, Genesys, ADS & friends can do and that Spice cannot.

have a good night, Gerhard

Am 03.03.2017 um 21:28 schrieb Kevin Aylward:

I agree. There is next to no incentive for any company to develop a spice for non ic design applications.

NGSpice is a very good choice. It includes XSpice anyway. Its got quite a lot of good new stuff. There are even smutterings of adding PSS.

I wrote SS to give me personally, in part, affordable ic design features. Worst Case corner support on its own, for me, is justification to never use LTSpice. Nothing I do has any meaning without ensuring it will work over all process corners.

As far as development in XSpice, if anyone wants my MS VC++ full code of my XSpice version for free, just ask. I consider my value added is my GUI.

-- Kevin Aylward

I believe KiCad now integrates NGSpice.

That's my main bitch about LTSpice: the GUI. The circuits look butt-ugly IMO. I did test a lot of other flavours of Spice out back in the day and they nearly ALL had much nicer user interfaces than LT; some really pretty. Still, you can't complain too much about something that works pretty damn well and costs nothing!