Development of Two-Stage Quartz-Crystal Oscillators Using Monolithic Four-Terminal CFOAs

In this article, based on the well-known circuits of two-stage quartz-crystal oscillators, three electronic circuits with a small number of external components are presented. For the proposed circuit configurations, the active elements are composed of monolithic current-feedback operational amplifiers (CFOAs) with access to terminal z, between the first stage (positive second-generation current conveyor (CCII)) and the second stage (output buffer). In this way, the output signal for the developed circuits is obtained after the output buffer of the second CFOA, thereby providing a minimal effect on the resonant circuit of the oscillators. Based on a theoretical analysis of the operational principle for the proposed circuits, the linear characteristic equations and the related self-oscillation conditions are obtained. Moreover, the frequency stability coefficients are determined, which can be obtained with larger values compared to the coefficients of the known discrete transistor circuits. To verify the operability and efficiency of the proposed oscillator circuits, experimental results obtained from sample electronic circuits are presented, which confirm the analyses performed in the frequency range up to about 10 MHz