ABSTRACT
Figure 42 above shows the high center frequency at 557 Hz, that calculated above with Sen3 for R3 > 0, while the remaining components have sensitivities < 0. If we were to recalculate the extreme center frequency using Sen3 < 0, as in an FMCA, all components would then have the low tolerance assigned as in the following:
fah := ~ R3·0.98·C1~0.9·C2·0.9 { R1·~.98 + R2·~.98) p
fah = 568.4 All Sen> 0 We find this combination produces a higher center frequency (568.4) than the S<H:alled EVA high. This is exactly what happens when an FMCA is performed. One final comment about this circuit before proceeding to an FMCA. Notice that the design center frequency amplitude was 10V. The precise design values for the components were as follows (see Reference 11.):
R1 := 15915.49
R4 := 3296.5
R2 := 5064.6
R5 := 13185.99
R3 := 2637.2
With the exception of R1, the four resistor sensitivities are> 10 at F = 500 Hz. Hence when converting to the standard 1% values, the desired amplitude was not achieved. In fact it was quite far off:
This is another drawback of this design, though not necessarily of this topology.
