Bootstraping Op Amp substrate for lower Distortion - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 26th January 2003, 04:27 PM   #1
ppl is offline ppl  United States
diyAudio Member
 
ppl's Avatar
 
Join Date: Apr 2001
Location: Seattle, WA U.S.A.
Default Bootstraping Op Amp substrate for lower Distortion

The Analog device Application note AN-232 describes a method of bootstrapping the substrate of fet input Op Amps. The reason claimed is that a reduction in THD can result from using this method with mismatched input impedances on the Op amp’s inputs. The Bootstrap method apparently keeps the common mode voltage constant in the Fet input and thus reducing the nonlinear capacitance change with the signal. the note http://www.analog.com/UploadedFiles/...22599AN232.pdf

I would like to get more opines on this.
  Reply With Quote
Old 26th January 2003, 05:16 PM   #2
dimitri is offline dimitri  United States
diyAudio Member
 
dimitri's Avatar
 
Join Date: Oct 2002
Location: retired
Send a message via ICQ to dimitri
Please, can you read this JVC paper
Feedforward Floating Power Supply (High Response Speed Equalizer Circuit)
Vol. 30, Number 5 pp. 324 (1982)
Author: Eiichi Funasaka
Author: Hikaru Kondou
Abstract: A method for drastically reducing nonlinear distortion and transient intermodulation distortion in noninverting unity-gain amplifiers is described. The method uses a floating power supply with feedforward and boot-strap techniques.
There are some measurement
The original idea was published in Wireless World. I will find it later.
  Reply With Quote
Old 26th January 2003, 05:30 PM   #3
dimitri is offline dimitri  United States
diyAudio Member
 
dimitri's Avatar
 
Join Date: Oct 2002
Location: retired
Send a message via ICQ to dimitri
OK, the bootstrapping of the op amp supply rails was proposed by Sandman in Wireless World, vol. 80, pp.367-371 (1974 Oct) "Reducing amplifier distortion" but without explanation, as I remember. It is nice method for decreasing distortion in slow op amp based follower, may I repeat myself, only follower. I had used it in a past ... the follower then a noninverting amp (_gainclone_)
  Reply With Quote
Old 26th January 2003, 06:10 PM   #4
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
In the good old days we used to be able to get
JFET and MOSFET parts with the substrate pin
available so you could do this discretely.
  Reply With Quote
Old 27th January 2003, 02:06 AM   #5
alvaius is offline alvaius  Canada
diyAudio Member
 
Join Date: Feb 2002
Location: Toronto
Yes this technique seems to work quite well. If you look at the distortion measurements on almost any op-amp data sheet it in in inverting configuration. However, at the input to your pre-amp, amp, an inverting input is usually not possible due to the low input impedance.

I use a circuit similar to the one in the ADI app-note for general purpose applications. It sounds quite nice. There is another thread on non-inverting op-amp distortion. I posted a schematic over there.

Alvaius
  Reply With Quote
Old 27th January 2003, 06:35 AM   #6
dimitri is offline dimitri  United States
diyAudio Member
 
dimitri's Avatar
 
Join Date: Oct 2002
Location: retired
Send a message via ICQ to dimitri
I post both ideas. In W.Jung circuit the output slew rate is equal to the slew rate of first follower and cannot be improved. In JVC circuit it can be 10-100 times higher as the frequency compensation capacitors are also bootstrapped. The simple discrete BJT follower can be used for bootstrapping. If the input capacitance linearity is the issue, the more complex follower can be used (actually it has feedback bootstrapping).
Mr. Pass, it is nothing to do with substrate pin, it works like the second (opposite) gate and should be connected to source. Both source and drain should be bootstrapped.
  Reply With Quote
Old 27th January 2003, 06:37 AM   #7
dimitri is offline dimitri  United States
diyAudio Member
 
dimitri's Avatar
 
Join Date: Oct 2002
Location: retired
Send a message via ICQ to dimitri
figures
Attached Images
File Type: gif bootstrapping.gif (4.9 KB, 593 views)
  Reply With Quote
Old 27th January 2003, 06:56 AM   #8
ppl is offline ppl  United States
diyAudio Member
 
ppl's Avatar
 
Join Date: Apr 2001
Location: Seattle, WA U.S.A.
dimitri can you post a link to that other thred and to the feedfoward concept. TIA
  Reply With Quote
Old 25th June 2003, 01:59 AM   #9
diyAudio Member
 
Join Date: Feb 2001
Location: earth
Default Sandman articles

Hi all
I am looking for a couple of articles from Mr Sandman
(mentioned here) on feedfoward and and Sandman class-S amps.
They were published in Wireless world magazine in
the 70s and 80s. Here is the information I have:

1. Sandman, Wireless World, vol. 80, pp.367-371 (1974 Oct) "Reducing amplifier distortion"

2. A.M. Sandman, ‘CLASS-S: A Novel Approach To Amplifier Distortion’, Electronic And Wireless World, pp. 38-39, Sept. 1982.

If someone has this, can you email a scanned copy, or snailmail?
I checked my local library, and they don't have WW

TIA
Yv
(tinearsnospam@operamail.com) - remove 'nospam'
  Reply With Quote
Old 25th June 2003, 06:09 AM   #10
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Default sandman

Yves, I may be able to help you. Send me your email.

Jan Didden
  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
does lower B+ cause scratchy distortion? PRNDL Tubes / Valves 0 20th June 2008 11:13 PM
Aleph L with huge distortion at lower settings? panos29 Pass Labs 3 15th May 2006 08:28 PM
Lower Distortion Alternatives to 12AT7 & 12AU7 ? DrDeville Tubes / Valves 19 20th May 2004 10:45 PM
Excel W12 lower distortion than W15?!? capslock Multi-Way 0 24th February 2004 11:34 AM
Expanded PTFE PCB substrate? Petter Parts 4 4th April 2003 12:34 PM


New To Site? Need Help?

All times are GMT. The time now is 11:50 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