Abstract: An RF transmitter (1) having a gate-segmented power output stage (2) and a digital driver (5). The gate-segmented power output stage (2) includes a field-effect transistor with a plurality of gate fingers (32) and drain fingers (31) that define a gate periphery. The field-effect transistor comprises a plurality of power output stage segments (3) that each correspond to a respective part of the gate periphery, and that each have a respective power output stage segment input (4). The digital driver (5) has control outputs (6) which are connected to corresponding ones of the respective power output stage segment inputs (4), and is configured for individually switching each of the power output stage segments (3) between an on mode and a cut-off mode in dependence of one or more input signals to obtain a modulated RF carrier signal at an output (7) of the gate-segmented power output stage (2).

Abstract: An RF power amplifier according to the invention comprises a plurality of parallel output transistors (HBT,1,1 to HBT,1,N) connected to a power supply. A plurality of base resistors (Rb,1,1 to Rb,1,N) for the output transistors (HBT,1,1 to HBT,1,N) and a plurality of input capacitors (Cb,1 to Cb,N), each coupled in parallel to receive an RF signal input and connected via at least one additional passive component to the inputs of each corresponding output transistor (HBT,1,1 to HBT,1,N), are provided. An output for an RF output signal is obtained from the parallelconnection of the output transistors (HBT,1,1 to HBT,1,N). The transistors (HBT,1,1 to HBT,1,N) are heterojunction bipolar transistors.