Robust GaN based LNAs with active epitaxial current limiters

In this letter, the current limiters fabricated by the Gallium Nitride (GaN) active epitaxial layers are introduced to achieve GaN based robust low noise amplifiers (LNAs). In principle, by taking the advantage of the current saturation effect, the gate DC current which causes gate degradation or breakdown can be controlled below the breakdown limit at any input level. The active current limiter can also reduce the on-state degradation by reducing the drain current. Two designs of robust LNAs in Ka-band are presented. The LNA1 has current limiters in gate regions, and the LNA2 has current limiters in both gate and drain regions. Both LNAs survive in a 1 hour stress experiment with 32-30.5 dBm input power. After the stress experiment, both LNAs show little degradation in noise figure; and the LNA2 shows little degradation in gain because of the drain current limiter.