Monolithic Device with Dual Capacitor and Varistor Functions

Abstract

Protective devices are needed in electronic systems to protect against voltage surges. In this paper, a monolithic device incorporating both the functions of a capacitor and a varistor is described. The device has a capacitance of 1 μF and a dissipation factor less than 0.05 between 1 and 100 kHz. At voltages greater than the threshold voltage, V 0 , of about 15 volts, the device conducts a current, I, according to the power‐law relation of varistors, I=AV α . The nonlinearity index, α, is 11.4. In this device, the capacitor function protects against the lowamplitude and high‐frequency transients while the varistor function protects against the high‐amplitude voltage surges. Appropriate capacitor and varistor composition can be found to have similar sintering temperatures, allowing the fabrication of monolithic devices with a range of sintering temperatures between 900° and 1350°C.