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I have a certain circuit and I want to see its ac performance when I send in certain noise as a signal. is there some option like noise source similar to sine etc signals in orcad....

I can make my noise file in excel an upload it as pwl signal, but i can run only transient analysis with it. I want to see the ac performance of my system.

I can generate noise by using some resistors at input, by this effects my later schematic.

is there a way to make a noise source other than these two options.....my frequency range is 100k to 220 Meg. and all my voltages would have a crest factor of 5.

to make it clear, i donot want to send noise by adding it to some kind of signal.instead i want to make noise as my signal.

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  • \$\begingroup\$ As far as I know, the spice AC-analysis does not use the signal at all, so this is not possible even if you find a noise source. If you want to see the frequency response for a "true" noise source, you have to model it with PWL, record a transient response and then take the FFT of this. I have not used pspice in over 15 years so I may be wrong. \$\endgroup\$ – pipe Apr 19 '16 at 14:54
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You can simply simulate the noise source as an ac source. For ac analysis, you're only looking at the small-signal effects from a single frequency component of any signal (noise or intentional) anyway.

all my voltages would have a crest factor of 5

Crest factor is a way of describing how your signals are shaped if they are not sinusoidal. It doesn't have any importance in an ac analysis of noise behavior.

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Assuming your circuit is linear, as The Photon says you can do your AC analysis with sines. What you have to do is analyze your target noise source and determine the energy content at frequencies of interest. Calculate the response at those frequencies and combine for the overall noise response.

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