Ultrastable quartz oscillators must be specially designed so as to match resonator parameters and electronic circuitry characteristics. Recently we have pointed out that our results have never been really resonator limited (at least for BVA units) and that further improvements would largely depend on progress in amplifiers. In order to improve the output signal stability of ultrastable oscillators it is necessary to reduce oscillating loop phase noise and to minimize phase noise of each stage of output amplifier as well. In this paper, each type of bipolar transistor amplifier configuration is considered: Common Emitter (CE), Common Collector (CC) and Common Base (CB). Power spectral density (PSD) of phase noise is calculated from the partial derivative of transfer function argument versus transistor and components parameters variations. In such a calculation, those variations are assumed to be uncorrelated. After this theoretical calculation, the PSD of each basic configuration (i.e., CE, CC, CB) is analysed. Results are compared and discussed taking into account criteria as stage gains, input or output impedances. Consequences are discussed in terms of amplifier performances and oscillator stabilities.
展开▼
