Power Amplifier Compression Compensation for Fewer Stacked Devices
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Solution Overview
Problem
Traditional power amplifiers face inefficiencies due to excessive voltage swings caused by choke coils, leading to the need for multiple stacked devices, which increases area and parasitic capacitance, resulting in signal loss and reduced efficiency.
Innovation Solution
A power amplifier system with a main amplifier and a compression compensating (CC) amplifier, utilizing series stacks of p-type and n-type transistors, along with AM-AM and AM-PM compensators to maintain linearity and reduce the number of stacked devices, thereby addressing voltage swings and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If an inductor is employed as a choke coil within the power supply path to supply power to the output stage, then the power supply function is achieved, but voltage and current ringing occurs causing excessive voltage swings at the output
Solution Approach 1:
The patent removes the inductor choke coil from the power supply path entirely. Instead of using a traditional inductor-based power supply network, the invention employs direct resistive coupling or alternative power delivery mechanisms that do not generate ringing, thereby eliminating the source of excessive voltage swings while maintaining power supply functionality to the output stage.
2Object-generated harmful factors
If an undesirably large number of output stage devices are stacked to counter excessive voltage, then voltage control is improved, but the area for the output stage increases and parasitic capacitance increases causing signal loss
Solution Approach 1:
The patent converts the harmful effect of voltage swings into a beneficial operating condition by designing the output stage to operate in a specific region where controlled voltage excursions are tolerated or even utilized. The complementary push-pull configuration with carefully biased transistors allows the circuit to handle voltage variations without requiring excessive stacking, thereby reducing area while maintaining voltage control.
3Object-generated harmful factors
If an undesirably large number of output stage devices are stacked to counter excessive voltage, then voltage control is improved, but efficiency is reduced due to multiple capacitive paths where signal is lost to ground
Solution Approach 1:
The patent applies different quality characteristics to different parts of the output stage. The complementary push-pull configuration assigns specific roles to n-type and p-type transistors, with each device optimized for its specific function. This localized optimization allows each transistor to operate in its optimal region, minimizing capacitive losses to ground while maintaining effective voltage control, thereby improving overall efficiency.
4Power
If N-type devices are employed in the output stage due to larger transition frequency and transconductance, then amplification performance is improved, but voltage and current ringing becomes problematic
Solution Approach 1:
The patent merges n-type and p-type devices in a complementary push-pull configuration. This combination allows the circuit to leverage the high transconductance and transition frequency of N-type devices while the P-type devices provide counterbalancing effects that suppress ringing. The complementary arrangement ensures that when one device conducts, the other is off, creating a push-pull action that maintains performance while reducing harmful oscillations.
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
Disclosed is a power amplifier system having a main amplifier with an input coupled to a main radio frequency (RF) input and an output connected to a main RF output, wherein the main amplifier exhibits a nonlinear gain characteristic with compression. At least one compression compensating amplifier has a signal input coupled to the common RF input and a signal output coupled to the common RF output.