Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Chip Amps Amplifiers based on integrated circuits

LM3886 overshoot
LM3886 overshoot
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
Thread Tools Search this Thread
Old 5th April 2012, 03:13 PM   #1
epilot is offline epilot  United States
diyAudio Member
Join Date: Jul 2006
Default LM3886 overshoot

Hello guys,

I have an LM3886 driving a capacitive load piezo at say 40KHz by a bandwith of say 10KHz.
the pirzo load has a capacitance of almost 0.2uF. I have the problem of ringigng/overshoot at the output of the LM3886 when connected to the said load (the load has an impedance of say 5ohms).Can you guys tell me how to remove/reduce the overshoot problem plz?
the datasheet of the chip suggest using an LR circuit in series with the load (0.7uH & 10 ohms). I did s but the result was not promising. ANy idea plz? did I used the wrong values of lr for my chip at the said freq?
By the way what about the Q of the L used here? How to choice it? I do not know if it is better to have a highe or the lower q for the L here?

Thanks a lot

P.S As my load is capacitive do I need to use any zobbel netwoork too?
  Reply With Quote
Old 5th April 2012, 04:25 PM   #2
KSTR is online now KSTR  Germany
diyAudio Member
KSTR's Avatar
Join Date: Jul 2007
Location: Central Berlin, Germany
Increase noise gain to 100x, 40dB (you don't need lowest THD, do you?).
Use a snubber as recommended (3R, 100nF or bigger) right on the chip from out to V-.
Isolate load with 1R or so (do you need max power transfer?).

Check application notes from Apex (now a sub-company of Cirrus), those are the best to found on most anything about power opamps. AN25, AN1, AN19.
  Reply With Quote
Old 5th April 2012, 04:37 PM   #3
jcx is offline jcx  United States
diyAudio Member
Join Date: Feb 2003
Location: ..
any narrow band transducer will ring, often peaking is deliberately designed for, it is used to increase efficiency

you need to understand the acoustic output requirements and the inherent limitations of narrow band transducers before you can optimally shape the driver impedance with external RLC, possilbly apply EQ

the min gain stability requirement of the decompensated chip amp is also possibly in play as memtioned
  Reply With Quote
Old 7th April 2012, 03:11 PM   #4
epilot is offline epilot  United States
diyAudio Member
Join Date: Jul 2006
Finall I could solve the problem of overshoot by putting a 70uH inductor in series with the piezo load.
the piezo as I said has a capacitance of 0.2uF and an impedance of 5ohms. But is it just right putting such a high inductor in series with the piezo load? The SPL of the piezo load seems to be higher by putting the said inductor. but I am afraid of damaging the piezo load by the inductor, Am I right? furthermore what will happen to the bandwidth of the load by putting such an inductor in series with the piezo load? I guess that the bandwidth would be reduced but I think I read somewhere that the bandwidth of the piezo load would be incrased by adding an inductor to the piezo loads. Any idea please?

  Reply With Quote


LM3886 overshootHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Overshoot and Ringing Captn Dave Tubes / Valves 25 21st January 2013 06:03 PM
Push-Pull SMPS overshoot problem circuit Power Supplies 83 7th June 2008 05:32 AM
Got an overshoot problem. Shoog Tubes / Valves 5 25th April 2008 05:09 PM
Are two separate lm3886 = 2*lm3886 in parallel or bridge mode rs1026 Chip Amps 11 21st October 2004 10:24 AM
Switching Mosfet overshoot tennisballg Class D 43 18th February 2004 11:17 AM

New To Site? Need Help?

All times are GMT. The time now is 07:00 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio