Simulation of the JE-990 OP Amp By Deane Jensen - Page 2 - diyAudio
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Old 30th August 2007, 02:45 PM   #11
PB2 is offline PB2  United States
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Quote:
Originally posted by mlloyd1
PeteB:

wow, great catch.
and thanks for the other info, too.

mlloyd1

Thanks mlloyd1!
I'm surprised that the patent was granted in the first place,
and that the prior art has not been mentioned before.

Pete B.
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Old 31st August 2007, 02:24 AM   #12
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Default Problem with MJE172/182 models

I tried a simulation run to measure the THD at 20 kHz with a 10 Vpp output into 600 ohms. The THD was .05 to .07 % which seems high for an advanced design like this. Note that I added a large (1000 uF) cap in the shunt path of the external feedback network for these sims to minimize DC offset at the output.

Checked the output bias, and the MJE172/MJE182 run around 50 uA quiescient current - this is not right. Tried MJE243/MJE253, MJ15034/15035, MJE340/350 and the quiescient current was 20 to 30 mA - much better, and the distortion was reduced by one to two orders of magnitude.

All the output models I tried are from OnSemi but it seems to me that the MJE172/MJE182 are defective. I checked the models and they are the current ones at the OnSemi site.

I then tried Fairchild output models for the BD139/140, MJE340/350 and these provided 15 to 20 mA.

The OnSemi BD139/140 provided 80 mA, which seems high.

The OnSemi MJE172/182 and BD139/140 do not seem right, but more work would have to be done to determine the problem.

This is just a preliminary look at this issue, just in case anyone is using the simulation. There are obviously several work arounds, find better models for the correct devices, or I would suggest using the MJE243/253 (similar vintage) or MJ15034/35 (modern) models from OnSemi.

I should have a look at the JE-990 sim at the Yahoo LT-Spice users group, and see what they use for outputs when I have some free time.

Pete B.
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Old 31st August 2007, 12:55 PM   #13
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Hi pete,

The JE-990 sim on the yahoo LTspice users group uses the MJE340/350 transistors as the output transistors.

Regards,
Ray
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Old 31st August 2007, 03:02 PM   #14
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Quote:
Originally posted by PB2
This patent should not hold up in court seeing as there was prior art as can be seen on page 38 of the .pdf in this link.
It's a moot point now. The patent has already expired.

se
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Old 24th September 2007, 01:35 AM   #15
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Quote:
Originally posted by rayfutrell
Hi pete,

The JE-990 sim on the yahoo LTspice users group uses the MJE340/350 transistors as the output transistors.

Regards,
Ray
Thanks Ray, I finally joined and did notice the file for that sim, will try to take a look at it soon.

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Old 6th October 2007, 11:04 PM   #16
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Default John Hardy at the AES 2007 Convention

I had the pleasure of meeting John Hardy yesterday at the AES Convention in NYC. Here's a bit more about him:
http://www.prosoundweb.com/recording...rdy_15_1.shtml

Pete B.
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Old 12th April 2012, 06:20 PM   #17
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PB2: Just download the je_990_plb_sim.zip file and opened in in LTSpice IV.
I wanted to see what it would show for input noise and got something in excess of 100nv/Sqrt(Hz) !
Wondering if you or anyone has revised your work to analyze noise? Maybe the modes used don't include noise? I used:
.noise V(Vout) V3 oct 10 20 20000
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Old 14th February 2013, 02:46 AM   #18
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Hi, just noticed your post, sorry for the delay.
I don't recall if the models have noise parameter info or not.
Have you read the original article on the design, the noise versus source
impedance is covered, IIRC.
It would also be interesting to look at the spectrum of the noise.
I've not done anything with noise analysis for this design.
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