kataria0 wrote on Mar 26th, 2009, 10:16am:About BW: As I mention "unity-gain buffer" of the op-amp, I meant op-amp with feedback acting as a buffer. The intended circuit is supposed to be linear (as linear as the specs). Just to make sure that this buffer doesn't become the bottleneck, its bandwidth is chosen to be 1.5MHz. So I just rolled up the bandwidths of the two components (first component not spcified but has a BW of 750KHz, second component is the buffer of 1.5MHz) in a RMS fashion to get an approximate answer.
of course your opamp is in feedback loop. The feedback i meant was the feedback from opamp to any other previous blocks. if there is no such feedback, then the overall system bandwidth is just roughly equal to the slowest block (error tolerance is not considered for this moment). i think that is also the opinion of rajasekhar.
kataria0 wrote on Mar 26th, 2009, 10:16am:About slewing: Slewing is dependent upon rate of change of input. Since sinusoid will have max dV/dt at zero crossing, the op-amp could slew momentarily and as a result cause non-linearity; not a desired property in linear systems, of course.
first, slew rate is the changing rate of the output, not input. second, the buffer opamp should be designed in such a way that its output swing can always sustain the signal amplitude, and the opamp is always in linear region. even momentarily entering nonlinear region is not accepted, otherwise large distortion will be introduced and the buffer is poorly designed.
i understand what you are worrying about, but that is not slew-rate. if your opamp is correctly designed (e.g. the output swing issue i mentioned), then the problem you are concerning is still within the scope of small-signal property, which is guaranteed by BW.