Multilayer varistors from AVX protect antennas and RF amplifiers from transients and ESD

Low capacitance of under 3 pF in 0402 chip sizes and less than 3 pF and 12 pF in the 0603 packages as well as low insertion loss make AntennaGuard varistors ideal for protecting the FETs used in miniature RF amplifiers against ESD damage. They are also suitable as a replacement for the output capacitors in cell phones, pagers and wireless LANs, with the added advantage of ESD suppression.

Antenna varistors offer a high degree of ESD repetitive strike capability compared to a SOT23 diode when subjected to IEC 61000-4-2 8-kV contact discharge.

By inherently replacing three devices (two zener diodes and an EMC capacitor), ZnO varistors require much less PCB real-estate. In RF applications AntennaGuard can offer savings in component volume up to 86 percent, and PCB footprint savings up to 83 percent.

In RF amplifiers it is common to employ some form of FET as they have nearly ideal input gate impedance and outstanding noise figure. However as trends towards higher efficiencies and smaller devices due to miniaturization these FETs are using ever thinner silicon dioxide layers to improve transistor gain and decrease size. However the downside is a higher susceptibility to ESD events as silicon dioxide layers thin out. AntennaGuard varistors are an ideal solution for protecting the FET and in addition to small size, offer superior performance to diode based methods, including better repetitive strike capability, higher in rush current capability, faster turn-on-time, and inherent EMI attenuation.