Simulating variable output impedance - 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 20th December 2007, 01:47 PM   #1
Account Disabled
 
Join Date: Jan 2006
Location: whereisit
Question Simulating variable output impedance

From an email I got from Analog Devices:

"The output impedance of the AD1955 analog output has a range of 20k - 80k ohms, depending on the signal level. This filter value should change linearly (inverse, as well) with respect to the capacitor value."

How do I simulate this in LTSPICE?
  Reply With Quote
Old 20th December 2007, 02:22 PM   #2
KSTR is offline KSTR  Germany
diyAudio Member
 
KSTR's Avatar
 
Join Date: Jul 2007
Location: Central Berlin, Germany
Ahem, this refers to the differential current outputs of the DAC?

Non-perfect current source could be simmed with a "resistor" parallel to a perfect current source. The value of the resistor must be made somewhat signal dependant, that means it must be constructed from behavioural sources, something along the lines of V=I(sense)*(20k+ 60k*F(signal)). Assuming that this F(signal) function is known...

Klaus
  Reply With Quote
Old 29th December 2007, 11:46 AM   #3
diyAudio Member
 
Join Date: Apr 2006
Location: Minnesota
abzug,

That quote from Analog Devices doesn't make any sense. The analog outputs are currents that depend on the digital input. The AD1955 should be used with an active current to voltage converter as shown on the data sheet. Doing this holds the voltage at the analog outputs constant.

Rick
  Reply With Quote
Old 30th December 2007, 06:47 AM   #4
Account Disabled
 
Join Date: Jan 2006
Location: whereisit
Quote:
Originally posted by sawreyrw
That quote from Analog Devices doesn't make any sense.
Sure it does. A perfect current source has infinite output impedance. A real one is finite, and in this case, it's signal-dependent.

Quote:
The AD1955 should be used with an active current to voltage converter as shown on the data sheet. Doing this holds the voltage at the analog outputs constant.
That's why I'm using Hawksford's I/V. However, no I/V can do this with absolute perfection, and in practice there will be a tiny voltage variation as a result. I want to simulate THD down to 0.1 ppm so I cannot ignore these effects.
  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
Variable operating biass output ? Bigun Solid State 133 15th August 2010 09:02 PM
Variable output SMPS Razor-Edge Power Supplies 7 3rd August 2007 11:37 PM
BOSOZ--variable impedance volume attenuator jh6you Pass Labs 22 15th March 2005 08:34 AM
First Watt-ish Chip Amp, Variable Impedance tgorham3 Chip Amps 3 13th February 2005 05:27 PM
Variable output impedence. JoeBob Solid State 1 20th June 2002 04:20 PM


New To Site? Need Help?

All times are GMT. The time now is 08:49 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