> > >If I remember correctly, and its been over 20 years since I've seen this, >but a 2 pole Gaussian low pass filter that is critically damped is the basis >for this number. That is the response that scope designers were trying to >design to. > >Tom Dagostino Which is where the common expression for the BW of a cascaded system (say a scope and a probe) came from. The sqrt of the sum of the squares formula, BW_sys = 1/SQRT(1/scope_bw^2 + 1/probe_bw^2), depends on the bandwidths of the system parts being assumed to have a gaussian frequency response. Today (as opposed to 20 years ago) high performance scopes (and probes) are usually designed to have a maximally flat frequency response. With the max flat response, the BW_sys = MIN(components_bw) as a 1st order approximation. (the composite BW is defined by the narrowest BW in the cascade) -Ray Anderson ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu