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Phase Shift and Feedback

Author: Leonard Krugman

One effect of the reactive components is to cause a phase shift between the input and output terminals. Phase shift reduces the in-phase component of the positive feedback signal. This is illustrated in Fig. 6-13 (A) where EF is the feedback signal and φ


Fig. 6-13. (A) Effect of phase shift on feedback signal.

is the phase angle between the input and output signals. EF1 represents the feedback amplitude at low frequencies when the reactive effects are negligible. As tke operating frequency is increased, EF2 and the input signal are no longer in phase. Thus, only the in-phase component of EF is useful for maintaining circuit oscillation. When the phase angle becomes so large that the in-phase component is less than the critical minimum required value, oscillation stops.

Last Update: 2007-03-21