A 2.4 GHz CMOS Doherty power amplifier with dynamic biasing scheme

Efficient amplification techniques for signals with high PAPR

“…When the input power increases, the main amplifier is saturated and the peak amplifier is turning on. To set the correct operating points of the power amplifiers a self-biasing [2] or an adaptive biasing [3] is used. An output impedance transformation network inverts load impedance in order to maximize the efficiency of the main power amplifier, when the peak amplifier is turned on.…”

A new wave of CMOS power amplifier innovations: Fusing digital and analog techniques with large signal RF operations

“…Many existing CMOS Doherty PAs are implemented using two RF amplifiers biased at different modes (for example, class-AB and class-C). Such designs typically suffer performance degradation due to the imperfect cooperation between the main and auxiliary PA [13][14][15]. Specifically, the auxiliary PA turning-on point and the relative gain between the two PAs achieved in practice can rarely match the desired relationship in the ideal Doherty operation.…”

“…Specifically, the auxiliary PA turning-on point and the relative gain between the two PAs achieved in practice can rarely match the desired relationship in the ideal Doherty operation. Though a few analog techniques have been proposed, e.g., asymmetrical main/auxiliary PAs [14] and dynamic biasing [15], this imperfect two-path cooperation still poses significant challenges.…”

“…These two RF signals are then separately amplified in the two PA paths, and the outputs are combined by the output transformer-based passive network. The output network simultaneously performs Doherty active load modulation, impedance down-scaling, and differential to single-ended conversion [15]. The digital code controls the two RF-DACs to turn on the proper power cells and synthesize the desired amplitude modulation (AM).…”

“…digital pre-distortion (DPD) [10][11] is a widely used method, as it is compatible with various PA architectures [12][13][14][15][16][17][18][19][20][21]. DPD requires a global feedback loop from the PA output to the digital baseband to compute and calibrate the distorted symbols.…”