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Plotting THD in db20 in Cadence

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Puppet123

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I want to plot THD in Cadence Spectre/Virtuoso.

THD in Calculator outputs a percentage.

So to do THD in dB20 I need to divide the calculated THD value by 100 and then take db20 of this - is that correct ?

Thank you.
 

You wrote in that other post:

"thd()" returns value as "%".

So 20*log10(10**(-10/20)/100)=-50dB

-10 is the value of the fundamental signal in this case ?

I am using Cadence version IC5 not IC6 without the Spectrum Assistant.

So does that mean once I get the THD value in percentage, I use db20(thd/100) in Cadence Spectre/Virtuoso calculator or I convert it to linear first and use the fundamental as you did above ?

Thank you.
 

Understand very basic things correctly.
This is very true for all your previous posts.

Spectre has no relation at all.

Learn and understand a definition of Cadence Skill Function, thd().
That’s all.
 
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As usual, you don't answer questions that are posted here.

Also, please respond in proper written english - your english language writing skills are very poor.

Just for others, since they might want to know, if you have 0.1% THD, this means that the amplitude of the fundamental is 1000 times larger than the amplitude of the harmonic components - since 100/1000 = 0.1%. So to get the THD in dB from the percentage just take 20 log of (0.1/100) - since you have to convert the percentage. So in Cadence, that would be dB20 (THD/100).

Then you get -60dB THD - as you should.

See, it's easy to actually answer a question.
 
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