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AD8031 PSRR Simulation in LTspice


for my next course about PSRR, I try to simulate the AD8031 PSRR with LTspice.

The used schematic is : 

Result is : 

This is very different from the datasheet graph (i.e. figure 35).

How explain that ?

Best regards.

  • Hi,

    as a complement, I've done a time domain analysis with that schematic : 

    It uses a BV source with 5V plus decade sinus (for 1k, 10k, 100k and 1MHz). Each spectral lines has a weight of -23dB in the FFT analysis. FFT on the output has given that result : 

    As you can see, this result is consistent with the AC analysis : the -88dB at 1MHz plus 23dB give -65dB which is the result at 1MHz with the AC analysis and so one for the other spectral lines.

  • Hi Eric, 

    Since you are using single supply, add a DC offset in the non-inverting input to use the whole range of input common-mode voltage range. Below is the PSRR graph obtained when I add 2.5V in non-inverting input. It resembles Figure 35 in the data sheet. Simulations are dependent on the part modeling and may present some limitations thus the low accuracy in the low frequencies.

  • Thanks a lot for you answer. You are totally right. I'm an idiot... I forgot the DC source which I already use in my final schematic.

    Have a good day.