ScienTECH AB65, Руководство по эксплуатации

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AB65
Scientech Technologies Pvt. Ltd. 7
Figure 1
A phase-shift oscillator can be built with one Op-Amp is shown above the normal
assumption is that the phase shift sections are independent of each other. Then
Equation is written
AB = A [l / RCs + 1]
3
The loop phase is -180° when the phase shift of each section is -60°, and this occurs
when
ω
= 1.732 / 2
π
RC because the tangent of 60° = 1.732. The oscillation frequency
with the component values shown in figure 1 is slightly different than the calculated
oscillation frequency. These discrepancies are partially due to the component
variations, but the biggest contributing factor is the incorrect assumption that the RC
section does not load each other. This circuit configuration was very popular when
active components were large and expensive, but now Op-Amps are inexpensive and
small and come four in a package, so the single op-amp phase-shift oscillator is losing
popularity.