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Old 18th May 2012, 06:25 PM   #21
KSTR is offline KSTR  Germany
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Find it attached, rename from .TXT to .ASC.

It's not a self contained complete model, only a stub, but you can just copy it into your circuits and use it for basic AC stability analysis. Don't excect that input parasitics are reflected, you must add them manually if desired.
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File Type: txt LM3886_AC_model.txt (824 Bytes, 166 views)
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Old 19th May 2012, 05:46 AM   #22
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Quote:
Originally Posted by KSTR View Post
I contacted TI, now that we know that TINA also shows the problem.
Faulty SPICE model of LM3886? - Audio Amplifiers Forum - Audio Amplifiers - TI E2E Community
There's a positive response from TI on that forum, so maybe there's still hope.
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Old 19th May 2012, 01:43 PM   #23
KSTR is offline KSTR  Germany
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Yes, let's wait and hope the best.

Their comment on the OLG modelled unloaded is confusing me though, I see no big change with any load from 0.1R to 10R. The gain magnitude curve just barely moves, phase curve remains unchanged.
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Old 19th May 2012, 03:03 PM   #24
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Quote:
Originally Posted by KSTR View Post
Their comment on the OLG modelled unloaded is confusing me though, I see no big change with any load from 0.1R to 10R. The gain magnitude curve just barely moves, phase curve remains unchanged.
Yeah, loading shouldn't make much difference to OLG - it's a low-impedance, high-current output stage driving the load in any event. Loading definitely cannot alter the dominant pole, which is typically a miller cap between some internal VAS nodes.
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Old 19th May 2012, 04:38 PM   #25
jcx is online now jcx  United States
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actually open loop gain can change noticably with loading vs totally unloaded - factors of 2 aren't impossible


macromodeling has always been hit or miss - often the "new guy" may be assigned to familiarize him with the products - even if he's never bult a model before, hasn't even read the app notes on modeling

http://www.analog.com/static/importe...tes/AN-138.pdf

http://www.ti.com/lit/an/sbfa009/sbfa009.pdf

http://www.ti.com/lit/an/snoa265b/snoa265b.pdf

http://www.ti.com/lit/an/snoa247a/snoa247a.pdf

just checking the pin assignment on the op amp package shows any model with spice node "0" in it is suspect - particularly with any sub component of the model directly connecting form the op amp pins to Spice gnd

even the notes above often get this wrong with CM Z, leakage parts going to gnd

what is frustrating is the bad use of node "0"/gnd in modeling has been clear from before monolithic op amps and Spice - as early Philbrick/Analog Devices papers show input parasitics/compensation referenced to the power supply pins of the op amp modules

Last edited by jcx; 19th May 2012 at 04:55 PM.
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Old 21st May 2012, 07:03 AM   #26
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I've just checked the LM3875 using 'TINA' in the inverting mode. On Friday I checked for non-inverting operation and the THD was as expected.
In the inverting mode the distortion is vanishingly small (unrealistic). I expected it to be lower as that is how the LM3875 measures in real life, but not by quite so much!
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Old 10th September 2012, 02:11 PM   #27
gootee is offline gootee  United States
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A TI newsletter mentioned that an LM3886 spice model was released in August. Has anyone looked at it yet?

I just saw the TI newsletter last night. I tried to look at the spice files but the versions I got linked to were encrypted or something. It was too late for me to pursue, last night, and now I'm at work and can't. Has anyone seen the newest LM3886 model?
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Old 10th September 2012, 02:58 PM   #28
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The files are now dated 6th July, so they have been changed from when I looked first. Taking their TINA ref schematic (inverting, unity gain) and changing R(in) to 1k to give a gain of 10, still shows unreasonably low distortion of 5E-6% at 1kHz and 7.4E-6% at 20kHz, into a 4R load at 30V pk-pk output, so something is still not right.
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Old 17th March 2013, 10:38 AM   #29
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any news?
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Old 14th April 2013, 07:46 AM   #30
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You're all dead?
Anyway...Im not expert of simulators but i try to use lm3886 TINA and PSpice model and I can't run any.
In TINA the models, both downloaded from TI or the original in TINA,the macro model does not seem to absorb any current, Pspice instead return me nodes erros, finally importing compilated pspice model in LTspice return error on the first compiled line.
The only model i can use is the LM4780 in TINA, very similar to the lm3886 but i fear is not exactly the same.
Any suggestions?
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