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LMH2832: TI-PSpice tools bug report relating to harmonic source spectrum error detected in FFT plot

robert grange
Prodigy 31 points
Part Number: LMH2832

There seems to be limitations on the transient generator and number of parameters to control amplitude and phase coefficients! The program archive attached can not set all the generator frequencies with a variable and looking at the spectrum there is an error in the FFT plot which does not make sense 

The time domain plot looks OK at least represents more than 3 harmonics! The harmonics generated are well inside the capability of the LMH2832 to mimic the source spectrum

The FFT plot is missing information - if I replace the frequency variable with a real value I can get the correct spectrum - so there seems to be a bug. 

I need to control amplitude and phase of all the generators and the bug appears preventing the tool from correct measurements?

Notice the first generator is picking up the fundamental frequency OK but only the 4th harmonic (real  number) is able to pass in the simulation!

How can this be fixed and what is the reason for the missing spectrum if it is a user error - it would be nice to know? Can anyone advise?

Bob

  • 0
    TI__Mastermind 23385 points

    Hello Bob,

      Can you explain a bit more on this statement: "if I replace the frequency variable with a real value I can get the correct spectrum" How are you doing this? As an if you are manually entering in the harmonics, then the FFT generated is correct? So rather than the harmonic measurement coming from the LMH2832 and the circuit surrounding it, you are the one feeding this information?

      For most of our models, they unfortunately do not accurately model distortion or harmonic measurements. The following are the list of parameters we focus on and check for when modeling our parts: Frequency Response, Gain Parameters, Noise, Input Voltage Range, Output Voltage Range, CMRR, Input Resistance, Output Resistance, Quiescent Current, Supply Voltage Range, Power Down. 

    Thank you,
    Sima