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 (mm Wave) 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.