THDN (total harmonic distortion + noise ) simulation of the Op-Amp

[Junus2012]

hello friends

So far I was enquirer how to simulate or calculate the SNR.

Now I would like to ask you how to simulate the THDN (total harmonic distortion plus noise) of the operational amplifier.

Thank you and I appreciate very much your answers

 

[FvM]

Referring to the standard SPICE methods, hopefully provided by any SPICE based simulator:
- THD is determined in transient simualution with fourier analysis
- Noise in noise analysis (AC analysis)

 

[Junus2012]

Dear FvM

can you please give me the circuit setup of the THD simulation and signal conditions.

for me I am thinking that I will connect the op-amp as a buffer then I would apply a signal with a certain frequency the I apply the fourier transform at the output, isnt like it, please

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if I understand you right, it mean that we can not show the noise and the THD in the same time because the noise will not appear in the transient analyses. right?

 

[FvM]

You'll essentially apply a sine input signal and perform a fourier analysis for the respective fundamental frequency. The SPICE fourier analysis calculates also THD numbers.

The setup is up to your specification, because THD will vary with amplifier configuration, loop gain, input and output impedance and signal level.