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How to measure noise of an amplifier?

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Pipeline

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I'd like to measure noise of a chopper amp, but I have not tested noise befoe. Anyone can give me some suggestions? Thanks!
 

elbadry

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If you are using spectre:

Setup a noise analysis. Choose the output node, input source and frequency range. Then Run the noise analysis.

You can plot output noise voltage or input noise voltage versus frequency...

Concerning a chopper amplifier, I think you will need to use a PSS analysis followed by pnoise analysis...

Hope this helps
 

gszczesz

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One quick way with to visually see typical noise is to do Transient Noise. This will give you a visual of what the output noise would look like.

Otherwise, like said before, you could do PSS or PXD analyses, though for that you need a repeating input signal to produce a steady state output.

Greg
 

sunwiss

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measure or simulate?
 

Pipeline

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I mean in testing not simulation, thanks.
 

gszczesz

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Now that depends on what you want. If you are looking for 1-sigma noise voltage, then put a scope on it, turn on trace overlay and see how thick the bar gets for a specific DC input.

If you are looking for noise performance over frequency, hook up a spectrum analyzer and for a given DC input (i.e. set up the chopper as a follower and have it's output mid-rail) look at the spectral power.

If you want an agregate noise to relate to a rms noise voltage or a noise power, you need a power meter. Set the op-amp as a follower, put a power meter on the output but make sure it has a DC blocker on it. The power you read will be your noise power which can be related to a noise voltage.

If you are using the chopper for mid to high frequency signal processing and you want the noise figure of it, then use a Noise Figure module available for most spectrum analyzers. Put the caliberated noise source at the input and measure the noise power at the output.

Greg
 

xwcwc1234

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How to simulate the noise performance of chopping amplifier using Hspice ? Is it possible for Hspice to do noise simulation with switch and clock ?
 

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