LT spice question. THD of Sine genny

"martin griffith" a écrit dans le message de news: snipped-for-privacy@4ax.com...

What spice really do is an FFT, so make sure to have the right signal length to avoid spectrum leakages (i.e. a full number of periods minus one FFT sampling time).

Yes. Initially came across the problem with a low distortion oscillator circuit. No matter how I tried I couldn't get the circuit distortion down to less than .1%. Trick is to force '.tran' to use a timestep way below what it would naturally pick for itself. Results is a slower tran run but gives circuit waveforms consisting of vast numbers of data points. At 1kHz a fixed 10uS max timestep (say) gets you down to the -90dB area. eg. " .tran 0 100m 0 10u " john

Thanks for that

martin