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bogdan_borko 6th August 2006 08:41 PM

Circuit Maker <<questions>>
 
How to measure distortion in circuit maker 2000?
How to do Fourier analysis and measure harmonics in dB?

bogdan_borko 6th August 2006 08:59 PM

I hope you understood what i`m asking for...
I meant "Harmonic distortion".
thanks

Steven 6th August 2006 09:08 PM

Distortion in Circuitmaker 2000
 
2 Attachment(s)
Select Analog Mode in Simulation, then go to Analyses Setup (F8), enable Transient/Fourier analysis and click on that button. In Transient and Fourier Analysis Setup enable Fourier (check box). At this moment I have the default timing selected (5 cycles, 50 points per cycle). Use a sine generator in the circuit diagram as input, e.g. at 1 kHz. Probe the output, or any point in the circuit.
Default the fourier analysis shows a linear frequency scale as the X-axis and volts or amps on the Y-axis. Right click on the Y-axis to get a pop up where you can select Primary Y-axis with Magnitude in Decibels. Then adjust the scaling, normally in the left pane, to e.g. 20dB per division and adjust the offset to get the harmonics in the graph. Distortion is calculated from the ratio of the harmonics and the fundamental.

bogdan_borko 6th August 2006 09:29 PM

thanks a LOT!

What is a good result in these measurements?

bogdan_borko 6th August 2006 09:43 PM

2 Attachment(s)
this is not good...?
could you comment?

it is a push pull mosfet class a power follower I`m simulating... it has no feedback, classic source follower...

Steven 6th August 2006 10:01 PM

Your harmonics are more than 60 dB below the fundamental, so distortion is approximately 0.1%, not bad for an open loop design.

bogdan_borko 7th August 2006 09:49 AM

how did you calculated 0.1%?

sreten 7th August 2006 11:09 AM

Quote:

Originally posted by bogdan_borko
how did you calculated 0.1%?
Hi,

0.1% is a thousanth = 10 to the power - 3 x 20 = - 60dB.

From the graph 2nd and 3rd dominate so I'd say ~ 0.2%.

:)/sreten.

bogdan_borko 7th August 2006 12:10 PM

thanks a lot guys!

I`ve searched the forum but haven`t found much about
what harmonic affects the sound the most (I just now the 2nd harmonic is "good") and what harmonic should we look at when we design the amplifier...

ANy link will be helpfull.
thanx!

sreten 7th August 2006 12:17 PM

Hi,

wieght the harmonics thus for degradation :

(harmonic number)squared / 4.

so 2nd = same, 3rd = x 9/4, 4th = x 4, 5th = x 25/4, 6th = x 9, etc

For 1khz 20 khz = x 100 or + 20dB, higher harmonics cannot be ignored......

:)/sreten.


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