Oscillations and PM-AM noise analysis of harmonic oscillators using differentially connected MOSFETs

The paper is devoted to development and investigation of harmonic oscillators using a pair of differentially connected MOSFETs. Modern integral technologies provide the opportunity to manufacture the differential pairs of MOSFETs having the necessary characteristics and providing high accuracy of symmetric circuits manufacture. That is why the oscillators using pairs of differentially connected MOSFETs have such advantages as low modulation sensitivity and absence of even numbers harmonic components in the spectra of the oscillators' output oscillations. The approximate theoretical analysis of stationary oscillations and PM and AM noises characteristics of the oscillators with differentially connected MOSFETs is presented and illustrated by particular example of such oscillator characteristics calculation. The analysis is based on the approach to the oscillators' investigation, developed by S.I. Evtianov. Using of this approach gave the opportunity to present results of these oscillators analysis by means of rather simple formulae. The formulae for the oscillator regime and PM/AM noise characteristics calculation were obtained. The investigations of the basic wideband noise sources of the differentially connected MOSFETs and the of common current source on the oscillator PM and AM noise power spectral densities have been done. The results of these calculations for particular oscillator were compared with results of the digital simulation of this oscillator.