Things you should know about LTSpice - Page 9

ikoflexer · 04:10 PM

Use the forum search function and lookup the terms laplace ltspice and you will find a few posts. The gist of it is to insert a voltage dependent voltage source (E) whose value is set to a string of the form

laplace ((1+3183u*s)*(1+75u*s))/((1+318.3u*s)*(1+3.183u*s))

You'll have to check the formula above because I wrote it from memory and I don't trust my memory.

In ltspice, to set the value of any component you press the CTRL key and in the same time press the right mouse button on top of the component. That will open a dialogue, and you need to change the "value" field.

ikoflexer · 9th December 2009, 04:25 PM

Here, download this file and run in in ltspice. You should get a plot as shown.

ra7 · 9th December 2009, 04:34 PM

excellent!!!

just what i needed! will try it this evening.

thanks man!

unclejed613 · 9th December 2009, 11:06 PM

tnx, i'm still a bit "fuzzy" about the use of laplace sources, that helps a lot for me too.

ra7 when you get ready to test your phono preamp with physical test equipment, the circuit i provided above goes in front of the phono preamp (between the sig gen and the phono preamp) and approximates (+/- 0.1db) the pre-emphasis curve of the laplace inverse riaa sig source.

ra7 · 9th December 2009, 11:23 PM

got it unclejed613!

I've actually built the thing and for some reason the top end is down although it simulates well. That's when I thought I should look deeper into the RIAA accuracy. I was using convoluted methods to determine the accuracy.

gaetan8888 · 11th December 2009, 08:52 PM

Hello

How can we see a frequency response graph of an amp with LTspice ?

Thank

Bye

Gaetan

keantoken · 11th December 2009, 09:57 PM

Right click on the input voltage source and enter "AC 1" into the box labeled "AC Amplitude".

Then go so Simulate->Simulation cmd->AC Analysis

I usually choose "decade" with 10 points per decade.

- keantoken

gaetan8888 · 11th December 2009, 10:15 PM

Hello keantoken

It's working

Thank a lot

Bye

Gaetan

mightydub · 12th December 2009, 03:00 AM

Quote:

Originally Posted by keantoken

Right click on the input voltage source and enter "AC 1" into the box labeled "AC Amplitude".

Then go so Simulate->Simulation cmd->AC Analysis

I usually choose "decade" with 10 points per decade.

- keantoken

That will give you the closed loop response. For the open loop response (for determining stability) see LoopGain.asc and LoopGain2.asc in the ...LTSpiceIV/examples/Educational directory.

both have references, find them on the web and read them for understanding.

eyoung · 20th December 2009, 08:25 PM

Hola Y'all...

Does anyone have a spice model for a TL431 programable precision reference??? Or know where to find it??

Freezing in SC, Elwood

9th December 2009, 03:50 PM	#81
ikoflexer diyAudio Moderator Join Date: May 2008 Location: Toronto	Use the forum search function and lookup the terms laplace ltspice and you will find a few posts. The gist of it is to insert a voltage dependent voltage source (E) whose value is set to a string of the form laplace ((1+3183us)(1+75us))/((1+318.3us)(1+3.183us)) You'll have to check the formula above because I wrote it from memory and I don't trust my memory. In ltspice, to set the value of any component you press the CTRL key and in the same time press the right mouse button on top of the component. That will open a dialogue, and you need to change the "value" field. Last edited by ikoflexer; 9th December 2009 at 04:10 PM.

11th December 2009, 09:57 PM	#87
keantoken diyAudio Member Join Date: Aug 2006 Location: Texas Blog Entries: 1	Right click on the input voltage source and enter "AC 1" into the box labeled "AC Amplitude". Then go so Simulate->Simulation cmd->AC Analysis I usually choose "decade" with 10 points per decade. - keantoken __________________ Contribute to the DIYAudio WIKI! http://www.diyaudio.com/forums/every...p-sign-up.html LTSpice wiki with special attention to new users' troubles

20th December 2009, 08:25 PM	#90
eyoung diyAudio Member Join Date: Aug 2007 Location: Sunny SC,USA 15 min south of Charlotte NC	Hola Y'all... Does anyone have a spice model for a TL431 programable precision reference??? Or know where to find it?? Freezing in SC, Elwood __________________ "when you open your mind to the imposible, soon you will find the truth...."

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9th December 2009, 04:34 PM	#83
ra7 diyAudio Member Join Date: Feb 2009 Blog Entries: 1	excellent!!! just what i needed! will try it this evening. thanks man!

9th December 2009, 11:06 PM	#84
unclejed613 diyAudio Member Join Date: Dec 2006	tnx, i'm still a bit "fuzzy" about the use of laplace sources, that helps a lot for me too. ra7 when you get ready to test your phono preamp with physical test equipment, the circuit i provided above goes in front of the phono preamp (between the sig gen and the phono preamp) and approximates (+/- 0.1db) the pre-emphasis curve of the laplace inverse riaa sig source.

9th December 2009, 11:23 PM	#85
ra7 diyAudio Member Join Date: Feb 2009 Blog Entries: 1	got it unclejed613! I've actually built the thing and for some reason the top end is down although it simulates well. That's when I thought I should look deeper into the RIAA accuracy. I was using convoluted methods to determine the accuracy.

11th December 2009, 08:52 PM	#86
gaetan8888 diyAudio Member Join Date: Apr 2007	Hello How can we see a frequency response graph of an amp with LTspice ? Thank Bye Gaetan

11th December 2009, 10:15 PM	#88
gaetan8888 diyAudio Member Join Date: Apr 2007	Hello keantoken It's working Thank a lot Bye Gaetan

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