A Cost - Based Path - Search Algorithm for Enhanced Design With Dynamic Bias

A novel algorithm for class-A/AB power amplifiers (PA) enhancement is fully described. The principle is to find a combination of base current (gate voltage), collector voltage (drain voltage) and input power for each output power level so that the linearity/efficiency specifications of the application are satisfied. Based on a 1tone static characterization of the amplifier, the algorithm uses a cost function that maximizes Power Added Efficiency (PAE) while minimizing gain variation, phase shift, and second and third harmonic power levels. The algorithm was applied to a pHEMT amplifier and a HBT transistor. Singletone measurements on the HBT transistor show an average PAE of 28% along the output power range, compared to the simulated 8% of a normal class-A.