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Measure OIP3 performance with LTspice

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szszjdb:
Dear All,

Is it possible to  measure OIP3 performance of an amplifier with LTspice? How is the procedure?
Attached the circuit ,FYI.

Best Regards,
James

szszjdb:
Dear All,

Does someone could give some advice?

Best Regards!
James?

rfclown:
I assume no one responded because there is not a straight forward procedure to measure OIP3. I suppose you'd have to do an FFT of the output waveform to see the level of the IM3 products.

mawyatt:
The two tone IMD is probably the simplest method, another method we used in early versions of Cadence was to sweep the input power and plot the fundamental vs the 3rd harmonic. Both methods however require an FFT, the first just a single FFT and the later many.

Remember doing both awhile back to get some idea of what to expect with actual hardware, one such circuit had some unique properties like gain expansion rather than compression at higher input levels.

Best,

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