Low-distortion Audio-range Oscillator - Page 85 - diyAudio
Go Back   Home > Forums > Design & Build > Equipment & Tools

Equipment & Tools From test equipment to hand tools

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 8th November 2012, 02:39 PM   #841
diyAudio Member
 
dirkwright's Avatar
 
Join Date: May 2011
Location: Virginia
Quote:
Originally Posted by rsavas View Post
Dirk,

Putting bypass caps on the opposite side of where the part lies is not recommended for good high freq decoupling. Vias create problems as they have inductance, something that you do not want for good de-coupling. Maybe the larger bulk decoupler (1uF) may go on the opposite side, but the smaller ones should be on the same side as the IC. The layout rules usually goes to put the smaller cap closest to the pin followed by the larger ones. Say 1nF,100nF,1uF. Using TH caps is not recommended as they take up a lot more space than a SM caps do, leading to more trace inductance. Choose X7R dielectric for the big ones and COG for the smaller ones, is usually recommended.The trace is to flow through the caps hi side, then finally to the IC pad/lead, with minimal trace length, in other words, no stubs. 0805/0603 are great for this. I agree, not that easy for a bread board design or discrete wiring prototype.

Rick
OK, thanks. I did not know that. This makes it even harder to use this SMD opamp because it's so small that it's hard to get all the SMD resistors and other components really close to the pins if there are power supply bypass caps in the way. I don't think the LME49990 is good for DIY design, even if I design my own boards. I'm going to try though. This is getting off topic though.
  Reply With Quote
Old 8th November 2012, 03:28 PM   #842
rsavas is offline rsavas  Canada
diyAudio Member
 
Join Date: Aug 2012
Location: Ontario
Lets not generalize if a part is good for DIY or not, a lot depends on the design of the PCB, regardless what the application is. Yes you can argue that some DIY's are not well versed in layout or SMT soldering, but that can also apply to many seasoned EE's in a professional capacity. It really depends on your experience, regardless of your credentials.
Rick
  Reply With Quote
Old 8th November 2012, 08:56 PM   #843
diyAudio Member
 
dchisholm's Avatar
 
Join Date: Mar 2011
Location: St Louis, Mo
Quote:
Originally Posted by rsavas View Post
The layout rules usually goes to put the smaller cap closest to the pin followed by the larger ones. Say 1nF,100nF,1uF. Using TH caps is not recommended as they take up a lot more space than a SM caps do, leading to more trace inductance. Choose X7R dielectric for the big ones and COG for the smaller ones, is usually recommended.The trace is to flow through the caps hi side, then finally to the IC pad/lead, with minimal trace length, in other words, no stubs. . . .
Rick,

By any chance can you suggest some appropriate mfgr's part numbers, and a suggested PWB layout sketch for power supply decoupling in an application like this? I vaguely recall some other forums where somebody tried to use the LME4990 and had stability problems. They concluded it was interaction between the opamp's inherently high gain-bandwidth product, and the PWB layout. Would be helpful to see a layout geometry that's known to work.

Dale
  Reply With Quote
Old 8th November 2012, 09:03 PM   #844
KSTR is offline KSTR  Germany
diyAudio Member
 
KSTR's Avatar
 
Join Date: Jul 2007
Location: Central Berlin, Germany
Quote:
Originally Posted by KSTR View Post
looks like Samuel was right and the shown results were unreal in terms of absolute levels. The synced averaging and the AP graphing methods are to be taken with a grain of salt.
I now finally figured how this works with only little attenuation of the spectral lines, although on the AP2322 (Sys2) this time -- won't matter much. Damn Win7 won't run the old APWin for some reason, so I post this next time I'm on XP again. I also measured the close-in behaviour of Viktors' oscilllator, no problem there that I could identify, will post that, too.
  Reply With Quote
Old 9th November 2012, 02:02 PM   #845
rsavas is offline rsavas  Canada
diyAudio Member
 
Join Date: Aug 2012
Location: Ontario
Hi Dale,
Look at Owen's thread,
http://www.diyaudio.com/forums/headphone-systems/179298-wire-ultra-high-performance-headphone-amplifier-pcbs.html
For parts, there are litterly 100's of possibilities, go to Mouser and search/filter for
capacitor-smt-mlc-50V-1u-X7r
capacitor-smt-mlc-50V-100n-X7R
capacitor-smt-mlc-50V-10n-NPO(COG)
Owen's threads have part #'s (BOM's)
A number of IC mfg have app notes on hi-speed layout design techinques. I know TI /Intel have many. I will attach some that I have sitting on my jump drive.
You can also look at my thread for my layout of the LME49830 as well,
http://www.diyaudio.com/forums/solid-state/220962-lme49830-latfet-yet-another-design-review.html
and Owen's LME49830 LatFET design,
http://www.diyaudio.com/forums/solid-state/196932-wire-amp-class-ab-power-amplifier-based-lme49830-lateral-mosfets.html
Attached Files
File Type: pdf Considerations for proper Layout of HS PCB's.pdf (365.8 KB, 44 views)

Last edited by rsavas; 9th November 2012 at 02:05 PM.
  Reply With Quote
Old 9th November 2012, 02:04 PM   #846
rsavas is offline rsavas  Canada
diyAudio Member
 
Join Date: Aug 2012
Location: Ontario
Some more
Attached Files
File Type: pdf High-speed PCB Design Considerations.pdf (795.1 KB, 57 views)
  Reply With Quote
Old 9th November 2012, 02:13 PM   #847
rsavas is offline rsavas  Canada
diyAudio Member
 
Join Date: Aug 2012
Location: Ontario
Default Good de-coupling

I have attached pic of the LME49830 layout, showing the PS decoupling, hope this helps.
Ground planes are so important, in some of the hi-speed design layouts we did in the past, we used NELCO material and stacked up the PCB, having very small distances between planes, so that they acted as distributed capacitance layers, sandwich power planes between ground planes. One design we used 16 layers with a number of embedded power/ground planes. This was done in 0.062" total thickness for a PCI FF PCB. I'd have to look at the stackup again to find the material specified, but you should get the idea.
Rick
Attached Files
File Type: pdf LME49830 decoupling.pdf (67.5 KB, 76 views)

Last edited by rsavas; 9th November 2012 at 02:22 PM.
  Reply With Quote
Old 13th November 2012, 06:31 AM   #848
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
Default never mind

Quote:
Originally Posted by RNMarsh View Post
thd is high -- dc specs are very good. Neds to be included within gnfb loop.
never mind - thinking of different P/N.
  Reply With Quote
Old 15th November 2012, 05:09 PM   #849
diyAudio Member
 
Join Date: Jun 2005
Location: Zürich
Related to this topic (no worth starting another thread): I've had the chance to scan the manual of the calibration fixture (067-0938-00) which was used to verify distortion performance of the Tektronix SG505. The PDF is made available here:

067-0938-00 - TekWiki

Good inspiration for those interested in building a passive notch filter!

Samuel
  Reply With Quote
Old 15th November 2012, 05:34 PM   #850
1audio is offline 1audio  United States
diyAudio Member
 
Join Date: Mar 2004
Location: SF Bay Area
Blog Entries: 3
That's a huge file for a manual. Thanks for making it available. It illustrates the complexity necessary to make something that is flexible. The switching looks like its similar to a Tek attenuator switch.
__________________
Demian Martin
Product Design Services
  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
Radford Low Distortion Oscillator Series 2 audiomik Equipment & Tools 21 19th February 2014 10:46 AM
ultra-low distortion audio oscillator geekysuavo Analog Line Level 16 26th March 2013 03:04 PM
Low distortion oscillator? rjm Equipment & Tools 30 4th May 2011 10:45 PM
Can we improve this low distortion sine oscillator ? gaetan8888 Solid State 22 29th March 2009 12:30 PM
Simple, low distortion 1kHz oscillator jackinnj Solid State 4 6th October 2003 03:58 AM


New To Site? Need Help?

All times are GMT. The time now is 02:32 PM.


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