Development of Self-Limiting LC Oscillators Using Cascade Structure of Monolithic CCIIs

I. Pandiev (Tech. Univ. Sofia, Bulgaria)

This paper presents the structure, and principle of operation of two circuit configurations of self-limiting LC oscillators using monolithic positive second-generation current conveyors (CCII+s), that are implemented with Current-Feedback Operational Amplifiers (CFOAs) with available compensation pin (Z). The proposed LC oscillators are synthesized using a systematic approach in the design of analog electronic circuits and can be considered as variants of the basic three-point oscillators, implemented with transistors (BJTs or FETs). Based on the analysis of the structure and electrical parameters of the CFOAs with compensation pin (Z), electronic circuits of oscillators with two-stage amplifier blocks are synthesized. The characteristic equations and self-oscillation conditions are derived for the obtained analog circuits, and recommendations for designing circuits with arbitrary frequencies are defined. To verify the efficiency of the proposed LC oscillators, an experimental study is performed in the frequency range from 100 kHz to 10 MHz. The CFOAs AD844A with an external terminal z of the internal current conveyor are used as active elements. The obtained experimental results well match the results of simulation modeling of the circuits and the parameters based on the derived analytical expressions.