Hi All,
This has me confused, because it should be childishly elementally trivial. :-\
I have a weird problem with a *trivial, trivial* circuit within LTSpice 17.0.31 for OSX. I ran across this while simulating something more involved and couldn't get THD down to anything like a sane value.
The pared back test circuit (attached) has a SINE 'Input', a 10k/10k voltage divider, with the 'Output' at the node between the 10k resistors. I thought I'd see 0.0000000% THD for both input and output, but I see:
Input: 0.720625%; and
Output: 2.1555337%
I can't figure out why, but wondered whether this might be a bug of some kind (either with me(!), or with LTspice).
I have:
.param Freq 1k
.fourier {Freq} 10 2000 V(Input)
.fourier {Freq} 10 2000 V(Output)
.opt plotwinsize=0 numdgt=15
.tran 30s
Input is set to: SINE(0 1 {Freq})
In the FFT trace, I see various peaks below the fundamental, at -90dB(*) and below, which doesn't match my expectation.
I may be having a breakdown, but if I'm not - does anyone have some pointers? Is this perhaps a known issue, or my expectations are perhaps askew?
Many thanks,
Ross
---
(*) - My bad - I originally posted -30dB
This has me confused, because it should be childishly elementally trivial. :-\
I have a weird problem with a *trivial, trivial* circuit within LTSpice 17.0.31 for OSX. I ran across this while simulating something more involved and couldn't get THD down to anything like a sane value.
The pared back test circuit (attached) has a SINE 'Input', a 10k/10k voltage divider, with the 'Output' at the node between the 10k resistors. I thought I'd see 0.0000000% THD for both input and output, but I see:
Input: 0.720625%; and
Output: 2.1555337%
I can't figure out why, but wondered whether this might be a bug of some kind (either with me(!), or with LTspice).
I have:
.param Freq 1k
.fourier {Freq} 10 2000 V(Input)
.fourier {Freq} 10 2000 V(Output)
.opt plotwinsize=0 numdgt=15
.tran 30s
Input is set to: SINE(0 1 {Freq})
In the FFT trace, I see various peaks below the fundamental, at -90dB(*) and below, which doesn't match my expectation.
I may be having a breakdown, but if I'm not - does anyone have some pointers? Is this perhaps a known issue, or my expectations are perhaps askew?
Many thanks,
Ross
---
(*) - My bad - I originally posted -30dB
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