As 5G is rapidly growing, wireless
communication systems require wideband, compact and highly efficient power
amplifier modules (PA) to drive the base station antenna arrays. Doherty PAs
are implemented in most base stations. The final stage in these power amplifier
modules has high supply voltages (28-50 V) to generate a high output power of
>20 W at reasonable output impedance levels. This work replaces the
‘classical’ single-ended cascode PA to drive the Doherty PA, with a series push-pull
(or totem-pole) PA to increase the efficiency and bandwidth of the driver. The
series push pull designs can reach peak efficiencies of 70.7%, which is about
10 percentage points higher than the efficiency of the single-ended PA. To
ensure that a fair comparison is made between the designs, the series push-pull
designs operate at 5 V and 10 V supply, in order to generate an output voltage
swing of 5 V and 10 V respectively. This is compared to the single-ended PA
with a 5 V supply and 10 V output swing. Simulation results show that the
series push-pull design does indeed increase the efficiency of the driver
whilst having minimal AM-AM distortion (<1 dB) at the design frequency of
3.6 GHz.