Varicond

Varicond 

(variable condenser), a ferroceramic condenser with sharply pronounced nonlinear dependence of capacitance on the voltage supplied to the capacitor plates. As the voltage increases, the dielectric constant, and hence the capacitance, reach a maximum (at an electrical field intensity of about 50-250 volts per mm inside the varicond) and then decline. The degree of nonlinearity and the capacitance of the varicond are greatly dependent upon temperature: as the temperature rises to the Curie temperature (for ferro-ceramics used at temperatures of 25°-200° C), the nonlinearity and capacitance also increase, reaching their maximum value; as the temperature is raised further, capacitance drops sharply, and nonlinearity disappears.

The nominal values for capacitance of variconds are 10 picofarads to 1 microfarad, and the nominal ratio of maximum capacitance to initial capacitance is 2-20, given voltage changes in tens of volts. Variconds have great mechanical strength and can withstand vibration, shocks, and moisture. Their service life is practically unlimited. Peculiarities of the varicond include temporal and thermal instability of capacitance, limited range of operating frequencies and temperatures, and high values of dielectric losses.

Variconds are used in automation and in radio engineering and electronics, for automatic static remote control, for boosting electrical power (dielectric amplifiers), for parametric stabilization of current and voltage, and for multiplication, division, and modulation of frequency.

REFERENCE

Verbitskaia, T. N. Varikondy. Moscow-Leningrad, 1958.