Re: Slope limiter Filter
My first comment is, that the amplifier noise is mainly defined by the input stage and can be estimated rather accurately from amplifier data sheets.
Depending on the signal processing methods in your application, either a wide band noise voltage, expressed as RMS or peak-to-peak value, or a frequency dependant spectral noise voltage density may be interesting. Both quantities can be detemined by tunable filters and a voltage measurement. It's important to know the effective noise-bandwidth of filters for a correct scaling of spectral results.
Also a FFT measurement, availaible with most modern digital oscilloscopes can be used for noise densitiy determination, but due to the statistical nature of this measurements a strong averaging of results is necessary. If the noise voltage is low, an amplifier may be needed to achieve a sufficient signal.