LTSpice PSRR - diyAudio
Go Back   Home > Forums > Design & Build > Software Tools

Software Tools SPICE, PCB CAD, speaker design and measurement software, calculators

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 9th June 2013, 11:24 AM   #1
diyAudio Member
 
Join Date: Oct 2004
Location: Denmark
Default LTSpice PSRR

How do you measure PSRR in LTSpice?

Been looking all over for any info on eaxctly how to do it, but have had no luck sofar.

I just want a simple explanation on how to do it on a amplifier simulation and maybe also an example.

Thanks.
  Reply With Quote
Old 9th June 2013, 01:26 PM   #2
Mooly is online now Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Good question. I would imagine the calculation is the usual 20log (v1/v2) where one of the voltages is the ripple on the rails.

Here's an LTspice file showing noise on the rails and the corresponding amplifier output. You can set your supplies up in a similar way.

This is what you should see on the amp output.
Attached Images
File Type: jpg Capture 4.JPG (143.6 KB, 136 views)
Attached Files
File Type: zip M1 Ripple Rejection.zip (6.5 KB, 15 views)
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 9th June 2013, 01:46 PM   #3
jcx is offline jcx  United States
diyAudio Member
 
Join Date: Feb 2003
Location: ..
the .TRAN is always best - you can see nonlinear effects of bias cutting off, clipping

.AC analysis, adding the AC value to the existing DC Vsource lets you do a frequency plot - but like all .AC is only a linearized small signal evaluation around the operating point found at the start of the sim - no nonlinear effects will be seen
  Reply With Quote
Old 9th June 2013, 02:02 PM   #4
diyAudio Member
 
Join Date: Oct 2004
Location: Denmark
Then how do you make LTSpice calculate 20Log(v1/v2).

Tried to add a new trace and enter the equation, no luck. Maybe I am doing it wrong.

Hmm.
  Reply With Quote
Old 9th June 2013, 02:06 PM   #5
Mooly is online now Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
I wouldn't know how you would set LTspice up to calculate something like that... I'd just use a calculator
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 9th June 2013, 02:22 PM   #6
jcx is offline jcx  United States
diyAudio Member
 
Join Date: Feb 2003
Location: ..
.AC does display the Bode plot

for a .TRAN you can look at the waveforms in the FFT plot window, ratio the any signal's frequency component's magnitude, phase to the PS waveform's components with the cursors

Last edited by jcx; 9th June 2013 at 02:31 PM.
  Reply With Quote
Old 10th June 2013, 12:46 AM   #7
diyAudio Member
 
jazbo8's Avatar
 
Join Date: Jan 2011
Location: In Transient
PSRR Example

You can also try right-click on the trace and enter the plot expression manually, e.g., 20*log(V(n001)/V(n002)).
  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
Opamp PSRR lumanauw Solid State 10 12th March 2007 01:42 PM
PSRR and Crosstalk dgardner Solid State 4 20th June 2005 02:09 PM
How to predict PSRR ? Kilentra Solid State 6 9th July 2004 08:31 PM
Designing for PSRR ALW Solid State 19 16th June 2004 08:00 PM
topology and PSRR theChris Tubes / Valves 1 23rd August 2003 01:36 AM


New To Site? Need Help?

All times are GMT. The time now is 07:47 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