A 60-GHz Dual-Mode Class AB Power Amplifier in 40-nm CMOS

A 60-GHz dual-mode power amplifier (PA) is implemented in 40-nm bulk CMOS technology. To boost the amplifier performance at millimeter-wave (mmWave) frequencies, a new transistor layout is proposed to minimize the device and interconnect parasitics while the neutralized amplifier stage is co-optimized with input transformer to improve the power gain and stability. The transformer-based power-combining PA consists of two unit amplifiers, operating in Class AB for better back-off efficiency. To further reduce the power consumption and hence extend battery lifetime, one unit PA is tuned off in low-power mode. A switch is used to short the output of this non-operating unit PA to reduce the combiner loss and improve the efficiency. The PA achieves a measured saturated output power (P_SAT) of 17.0 dBm (12.1 dBm) and 1-dB compressed power (P_1dB) of 13.8 dBm (9.1 dBm) in the high-power (low-power) mode. The power-added efficiencies (PAEs) at P_SAT and P_1dB are 30.3% and 21.6% respectively for the high-power mode. Compared to Class A, the PA operating in Class AB shows 5.3% improvement in measured PAE at P_1dB with no compromise in linearity. The PA with the power combiner only occupies an active area of 0.074 mm ². The reliability measurements are also conducted and the PA has an estimated lifetime of 80613 hours.