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How to measure distortion in circuit maker 2000?
How to do Fourier analysis and measure harmonics in dB? 
I hope you understood what i`m asking for...
I meant "Harmonic distortion". thanks 
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 Xaxis and volts or amps on the Yaxis. Right click on the Yaxis to get a pop up where you can select Primary Yaxis 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. 
thanks a LOT!
What is a good result in these measurements? 
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... 
Your harmonics are more than 60 dB below the fundamental, so distortion is approximately 0.1%, not bad for an open loop design.

how did you calculated 0.1%?

Quote:
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. 
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! 
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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