STUDY OF INTERDEPENDENCE OF ELECTRICAL PARAMETERS OF VARICAP

Abstract

A varicap is a semiconductor diode whose operation is based on the use of the dependence of the capacitance on the reverse voltage and which is intended for use as an element with an electrically controlled capacitance. The barrier (charge) capacity of the p – n junction is used as the controlled capacity. Diffusion capacitance is not suitable for this purpose, as it manifests itself in the direct bias of the p-n junction, when the level of direct current through the diode is large, therefore, to control the value of diffusion capacitance, it is necessary to spend significant power of the power source. At the same time, changing the value of the barrier capacity when the varicap is turned on in reverse consumes very little power from the power source. In the production of varicaps, each type of device has several groups that differ in quality – low-quality and high-quality. The needs of varicaps in one or another group depends on the orders of consumers, which can change unpredictably. The quality of the varicap, like any capacitor, is determined by the ratio of the reactive resistance of the varicap at a given frequency of the alternating signal to the total active resistance of the varicap (loss resistance). It is shown that the resistance of the varicap structure depends on a large number of factors, many of which are not related to the measurement of the resistivity and thickness of the original epitaxial film. Therefore, it would be incorrect to focus only on the value of these two parameters when predicting the Q factor of the varicap. Based on this, there is a need to conduct research aimed at finding the dependence of the Q factor of the varicap on the values of some of its electrical parameters, namely, on the breakdown voltage and the capacitance overlap coefficient. This makes it possible to predict the Q factor of varicaps in the early stages of their production. The article presents the results of the study of the interdependence of the electrical parameters of the varicap. The dependence of the Q factor of the varicap on its breakdown voltage and the coefficient of overlap by capacity was investigated. Experimental graphs of the obtained dependencies are given. A methodology for predicting the Q factor of the varicap based on the values of its electrical parameters has been developed.