An analytical modeling is presented for the Colpitts and Clapp voltage-controlled oscillators, from which more precise equations are derived for calculation of oscillation frequency and small-signal negative resistance. Modeling is performed with taking into account a field-effect transistor parasitic capacitances. Finally, a comparison of start-up conditions is made for the Colpitts and Clapp oscillators verified by SPICE simulations. The derived equations assure a more accurate modeling, designing and implementing the Colpitts and Clapp voltage-controlled oscillators.

The paper describes a novel operational amplifier voltage controlled oscillator circuit which can be used in frequency range exceeding unity gain bandwidth. The voltage controlled oscillator topology is based on the operational amplifier negative capacitance converter. The voltage controlled oscillator architecture, mathematical modeling, ADS simulation results, and practical implementation are included. Results of measurements are also presented.

Розроблено математичні моделі та доведено теореми, що дозволяють визначити стаціонарний і нестаціонарний коефіцієнти оперативної готовності за довільного і експоненційного законів розподілу напрацювання системи до відмови. Доведено вирази, які, на відміну від відомих, враховують характеристики достовірності багаторазового контролю працездатності. Показано, що середній час напрацювання на незапланований ремонт системи багато в чому визначається ймовірністю помилкової відмови.

The simulation modeling algorithm is developed for evaluation of mean time between unscheduled removals (MTBUR) of periodically checked radio electronic systems. The general formulas are proposed for statistical evaluation of MTBUR. A comparison is conducted between the analytical and simulation modeling of MTBUR. A good agreement between the analytical and simulation results is observed.