V.N. Кuleshov - Dr.Sci. (Eng.), Professor, National Research University "MPEI". E-mail: vnk37@mail.ru
Т.I. Boldyreva - Ph.D. (Eng.), Associate Professor, National Research University "MPEI". E-mail: boldyrevati@yandex.ru
Е.М. Drozdova - Post-graduate student, National Research University "MPEI". E-mail: drozdovaem1989@mail.ru
А.А. Perfilyev - Ph.D. (Eng.), National Research University "MPEI". E-mail: perf@bk.ru

PM and AM noise in twin-T RC-oscillator consisting of differential amplifier, two "T" RC circuits, operating in parallel, inserted in negative feedback of differential amplifier, and amplitude limiting circuit, inserted in the positive feedback circuit, is investigated using abbreviated equations method, developed by S.I. Evtjanov. The amplifier used in the RC-oscillator model has low output impedance and voltage gain KU > 0, that is independent of frequency. The accurate and abbreviated symbolic equations of the RC-oscillator with feedback circuits - noise sources are derived. The steady-state operation equations are obtained and stability constraints are defined. The differential equations that define connection between noise sources and phase and amplitude fluctuations were derived. Simple formulae for PM and AM noise of this oscillator calculation are obtained. It is shown that PM noise of this oscillator is 5 dBc/Hz lower than PM noise of Wien bridge oscillator, having the same oscillation frequency, the same R and C values and the same output oscillation amplitude. The results of PM noise calculation in particular example of twin-T RC-oscillator is presented. The results of this paper can be used to explore opportunities to use RC-oscillators in the applications that are critical to their PM-noise level and compare different oscillators taking into consideration their PM and AM noise.

 

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