K-Band Hetero-Stacked Differential Cascode Power Amplifier with High Psat and Efficiency in 65 nm LP CMOS Technology

A K-band complementary metal-oxide-semiconductor (CMOS) differential cascode power amplifier is designed with the thin-oxide field effect transistor (FET) common source (CS) stage and thick-oxide FET common gate (CG) stage. Use of the thick-oxide CG stage affords the high supply voltage to 3.7 V and enables the high output power. Additionally, simple analysis shows that the gain degradation due to the low cut-off frequency of the thick-oxide CG FET can be compensated by the high output resistance of the thick-oxide FET if the inter-stage node is neutralized. The measured results of the proposed power amplifier demonstrate the saturated output power of the 23.3 dBm with the 31.3% peak power added efficiency (PAE) at 24 GHz frequency. The chip is fabricated in 65-nm low power (LP) CMOS technology and the chip size including all pads is 700 μm × 630 μm.