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Design >> Analog Design >> OP-amp HD5 is greater than HD3
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Message started by neoflash on Jun 28^th, 2013, 4:54pm

Title: OP-amp HD5 is greater than HD3
Post by neoflash on Jun 28^th, 2013, 4:54pm

I have a high speed class A/B amplifier whose HD5 is greater than HD3 in higher frequency. While in lower frequency, HD5 is about 6dB-10dB lower.

I never seen HD5 > HD3 before, anything can cause this?

Title: Re: OP-amp HD5 is greater than HD3
Post by Kevin Aylward on Jul 7^th, 2013, 1:52am

In general, this type of behaviour is intrinsically inherent in a power series expansion of a non-linear transfer function. Considering terms like a3.v^3 + a5.v^5, if the circuit does not clip on such large signals, the 5th order term will always, at some point, produce a larger level than its lower orders as the signal in increased.