Spice simulation - Page 60 - diyAudio
Go Back   Home > Forums > Design & Build > Software Tools

Software Tools SPICE, PCB CAD, speaker design and measurement software, calculators

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 10th July 2008, 09:07 PM   #591
lineup is offline lineup  Sweden
diyAudio Member
 
lineup's Avatar
 
Join Date: Dec 2005
Location: the north
Quote:
Originally posted by KSTR
From what I have looked at opamp models, I'd say the majority of models is pretty flawed in most aspects important for audio, above all distortion (which is *never* modelled) but also power supply effects (close to never modelled in a realistic way) etc. The twelve(!) year old model for the 134 is pretty coarse, probably not any good for detailed analysis of all but the most basic behaviour (AC stuff).

There are better models for newer opamps, anf for how close they are to the real thing they usually tell us precisly what is modelled and how deep.

The recent OPA211 is a good example, look how big it is and what they state in the header.
- Klaus
I know what you mean: 'pretty flawed'
And now we are speaking OP-amp models. And not transistors.

For example the default model of AD797 in my library is totally useless.
It shows nothing but ideal performance

I did run some tests of Open Loop with this OPA134 model.
It does not seems to be too bad:
- Open Loop gain: ~10.000
- Open Loop Unity gain BWidth: Like 8-10 MHz
- Current output where start to distort: ~35 mA peak


I would say it is more of an honest model.
At least many times better than my discusting AD797 spice model


Regars, Lineup
__________________
lineup
  Reply With Quote
Old 10th July 2008, 09:39 PM   #592
KSTR is offline KSTR  Germany
diyAudio Member
 
KSTR's Avatar
 
Join Date: Jul 2007
Location: Central Berlin, Germany
Er, AD797.... this one?
Quote:
* AD797 SPICE Macro-model 10/92, Rev. A
* AAG / PMI
*
* Copyright 1992 by Analog Devices, Inc.
*
* Refer to "README.DOC" file for License Statement. Use of this model
* indicates your acceptance with the terms and provisions in the License
* Statement.
*
* Node assignments
* non-inverting input
* | inverting input
* | | positive supply
* | | | negative supply
* | | | | output
* | | | | | decompensation
* | | | | | |
.SUBCKT AD797 1 2 99 50 38 14
*
* INPUT STAGE & POLE AT 500 MHz
*
IOS 1 2 DC 50E-9
CIND 1 2 20E-12
CINC1 1 98 5E-12
GRCM1 1 98 POLY(2) 1 31 2 31 (0,5E-9,5E-9)
GN1 0 1 44 0 1E-3
CINC2 2 98 5E-12
GRCM2 2 98 POLY(2) 1 31 2 31 (0,5E-9,5E-9)
GN2 0 2 47 0 1E-3
EOS 9 3 POLY(1) 22 31 25E-6 1
EN 3 1 41 0 0.1
D1 2 9 DX
D2 9 2 DX
Q1 5 2 4 QX
Q2 6 9 4 QX
R3 97 5 0.5172
R4 97 6 0.5172
C2 5 6 3.0772E-10
I1 4 51 100E-3
EPOS 97 0 99 0 1
ENEG 51 0 50 0 1
*
* INPUT VOLTAGE NOISE GENERATOR
*
VN1 40 0 DC 2
DN1 40 41 DEN
DN2 41 42 DEN
VN2 0 42 DC 2
*
* +INPUT CURRENT NOISE GENERATOR
*
VN3 43 0 DC 2
DN3 43 44 DIN
DN4 44 45 DIN
VN4 0 45 DC 2
*
* -INPUT CURRENT NOISE GENERATOR
*
VN5 46 0 DC 2
DN5 46 47 DIN
DN6 47 48 DIN
VN6 0 48 DC 2
*
* GAIN STAGE & DOMINANT POLE AT 7.33 Hz
*
EREF 98 0 31 0 1
G1 98 10 5 6 10
R7 10 98 10
E1 99 11 POLY(1) 99 31 -2.294 1
D3 10 11 DX
E2 12 50 POLY(1) 31 50 -2.294 1
D4 12 10 DX
G2 98 13 10 31 1E-3
R8 13 98 10
G3 99 14 98 13 34.558E-3
G4 99 16 98 98 34.558E-3
G5 14 15 15 14 20E-3
G6 16 17 17 14 20E-3
R9 15 18 400
R10 17 18 400
E3 18 98 16 98 1
R11 16 98 4.3406E8
C5 16 98 50E-12
V1 99 19 DC 2.2542
D5 16 19 DX
V2 20 50 DC 2.2542
D6 20 16 DX
RDC 14 98 1E15
*
* COMMON-MODE GAIN NETWORK WITH ZERO AT 1.35 kHz
*
ECM 21 98 POLY(2) 1 31 2 31 (0,158.11E-3,158.11E-3)
RCM1 21 22 1
CCM 21 22 1.1789E-4
RCM2 22 98 1E-6
*
* POLE-ZERO PAIR AT 3.9 MHz/10 MHz
*
GPZ 98 23 16 98 1
RPZ1 23 98 1
RPZ2 23 24 0.63934
CPZ 24 98 24.893E-9
*
* NEGATIVE ZERO AT -300 MHz
*
ENZ 25 98 23 31 1E6
RNZ1 25 26 1
CNZ 25 26 -5.3052E-10
RNZ2 26 98 1E-6
*
* POLE AT 300 MHz
*
GP2 98 27 26 31 1
RP2 27 98 1
CP2 27 98 5.3052E-10
*
* POLE AT 500 MHz
*
GP3 98 28 27 31 1
RP3 28 98 1
CP3 28 98 3.1831E-10
*
* POLE AT 500 MHz
*
GP4 98 29 28 31 1
RP4 29 98 1
CP4 29 98 3.1831E-10
*
* OUTPUT STAGE
*
VW 29 30 DC 0
RDC1 99 31 23.25E3
CDC 31 0 1E-6
RDC2 31 50 23.25E3
GO1 98 32 37 30 25E-3
DO1 32 33 DX
VO1 33 98 DC 0
DO2 34 32 DX
VO2 98 34 DC 0
FDC 99 50 POLY(2) VO1 VO2 7.56E-3 1 1
VSC1 35 37 0.945
DSC1 30 35 DX
VSC2 37 36 0.745
DSC2 36 30 DX
FSC1 37 0 VSC1 1
FSC2 0 37 VSC2 1
GO3 37 99 99 30 25E-3
GO4 50 37 30 50 25E-3
RO1 99 37 40
RO2 37 50 40
LO 37 38 10E-9
*
* MODELS USED
*
.MODEL QX NPN(BF=2E5)
.MODEL DX D(IS=1E-15)
.MODEL DEN D(IS=1E-12 RS=6.3708E3 AF=1 KF=1.59E-15)
.MODEL DIN D(IS=1E-12 RS=474 AF=1 KF=7.816E-15)
.ENDS AD797
  Reply With Quote
Old 10th July 2008, 09:57 PM   #593
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
I thought that today's SPICE models were 'perfect'.
  Reply With Quote
Old 10th July 2008, 10:08 PM   #594
diyAudio Member
 
Join Date: Sep 2006
Quote:
Originally posted by john curl
I thought that today's SPICE models were 'perfect'.

Hi John,

Who said that?

You certainly did not hear it from me.

Cheers,
Bob
  Reply With Quote
Old 10th July 2008, 10:09 PM   #595
diyAudio Member
 
Join Date: Sep 2002
Location: Sweden
Quote:
Originally posted by john curl
I thought that today's SPICE models were 'perfect'.

Are all real components perfect, just because some of them are very good?

It is difficult to make a really good model, and for complex things like op amps there is also the trade off between goodness and simulation speed. And let's not forget that the manufacturers also don't want to give us too many details about what's actually inside them. It would be interesting to know how good the in house simulators of AD, TI and others are. I understand they usually use better simulators than Spice also.
  Reply With Quote
Old 10th July 2008, 10:10 PM   #596
lineup is offline lineup  Sweden
diyAudio Member
 
lineup's Avatar
 
Join Date: Dec 2005
Location: the north
Quote:
Originally posted by john curl
I thought that today's SPICE models were 'perfect'.

John.
Some models are excellent.
It has been verified that they can predict real circuits very well.

But some models submitted, probably by manufacturers of products,
are far from reality.
To use them and get some valid results, would be a big mistake.

Just like any other model of reality - there are good and bad.

Take maps.
There are many different maps:
- road maps
- nature topology maps
- different resolutions

And maps can also be more or less precise.
With todays satellite based maps, we can get a very precise model / picture
of the real location.
Sometimes downto to less than 10 meter resolution.


talking of using virtual tools:
John, I am not actually conversating you.
This post is just a virtual conversation/communication I have with you and others.
Using a model of real speech.

Should not be confused with the real thing
... when you can do a listening test of my voice
... and see my facial expressions, while speaking with you
.

Sure there is a difference.
Isn't it?
__________________
lineup
  Reply With Quote
Old 11th July 2008, 03:06 AM   #597
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
Gee, fellas, I was just joking! I KNOW that most models are not perfect, and that is why when Bob Cordell demanded a SPICE model of my JC-1 power amp, (long ago) I just about fell over laughing.
I know a little something about models, as I used to have to make the transistors models myself with a curve tracer back in 1966, a long time ago. We had problems then, Dr Pederson (the father of SPICE) had problems in 1973, when I was taking his class, and we still have problems (some) now. I don't expect perfection, but I do not rely on imperfection to optimize my circuits in virtual space, either. It is just easier for ME just to try the circuit in real space.
  Reply With Quote
Old 11th July 2008, 03:32 AM   #598
andy_c is offline andy_c  United States
Banned
 
Join Date: Apr 2003
Quote:
Originally posted by john curl
Gee, fellas, I was just joking!
Thanks for clearing that up, John. For a minute there, I thought Grey might have broken into your account .

But seriously, most SPICE op-amp macro models are really awful. They do not model distortion at all, though they do exhibit some distortion because the input stage is usually modeled with discrete devices. We discussed that in the Blowtorch thread.

The discrete device models, at least for BJTs, are not so bad, and as Scott has mentioned, can be quite good when professional care is taken to extract the parameters. JFET models are pretty primitive, as there is currently no economic incentive for the development of better ones as there is with MOS devices. If you're interested in learning more about the equations that modern SPICE simulators use for BJTs, I highly recommend Massobrio and Antognetti. It's a great book. In fact, given that you're a "bookworm" kind of guy, I'm surprised that you haven't dug in and pointed out the errors that are often made. It's another world with many new horizons to discover.
  Reply With Quote
Old 11th July 2008, 03:44 AM   #599
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
We, old geezers, don't need to know about spice models to that extent, but thanks for the tip. I'm sure PMA will be interested, and several others. Since I design almost exclusively with Japanese Jfets, mosfets, and only sometimes use transistors, modeling transistors with Spice is not my first interest. Getting microcap to work easily, for me, is my best priority, and I will leave the models up to you engineers.
  Reply With Quote
Old 11th July 2008, 12:19 PM   #600
PHEONIX is online now PHEONIX  Australia
diyAudio Member
 
Join Date: Jul 2004
Location: Australia
Default Convergence

Hello andy_c

Just out of curiosity have you ever tried different simulators which have claims of better convergence and compared them too Ltspice using same circuit and models , other packages which I refer to are Spectre (cadence) and Simetrix. Dont get me wrong as freeware LTspice is very hard to beat its serious software.

Regards
Arthur
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Need help with Spice simulation overmind Everything Else 4 23rd December 2002 04:58 PM


New To Site? Need Help?

All times are GMT. The time now is 06:10 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2