Symmetric Doherty Amplifier With In-Package Combining and Shunt Inductance
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Solution Overview
Problem
Conventional Doherty power amplifiers face challenges in achieving balanced performance between gain, linearity, and efficiency, with symmetric configurations offering better gain and linearity but poorer efficiency, while asymmetric configurations have better back-off efficiency but poorer linearity and gain.
Innovation Solution
The design incorporates symmetric or slightly asymmetric carrier and peaking power amplifier devices with in-package combining nodes and a real combining load matching circuit, featuring a 50-ohm combining node impedance to eliminate the need for an output transformer, reducing parasitic effects and simplifying impedance matching, and utilizing a shunt-inductance circuit for improved video bandwidth performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If symmetric Doherty amplifier configuration is used, then gain and linearity are improved, but back-off efficiency deteriorates
Solution Approach 1:
The patent applies asymmetry by making the peaking amplifier larger than the carrier amplifier in a Doherty configuration. This asymmetric sizing allows the peaking amplifier to provide the additional current needed for high back-off efficiency while the carrier amplifier maintains the signal for linear operation, thus resolving the contradiction between maintaining linearity and achieving high back-off efficiency.
2Use of energy by moving object
If asymmetric Doherty amplifier configuration is used, then back-off efficiency is improved, but linearity and gain deteriorate
Solution Approach 1:
The patent employs dynamic load modulation through the Doherty architecture where the peaking amplifier's load impedance dynamically changes with signal level. At low power levels, the carrier amplifier sees a high impedance that maintains linearity. At high power levels, the peaking amplifier activates and provides a low impedance path, dynamically improving back-off efficiency while the carrier amplifier continues to operate linearly.
3Device complexity
If conventional symmetric Doherty amplifier is used, then impedance matching is simplified, but parasitic effects increase
Solution Approach 1:
The patent moves the combining node from the external package level into the internal die level, creating a three-dimensional integration structure. This dimensional change allows the combining node to be positioned close to both amplifier outputs, reducing the length of interconnect traces and minimizing parasitic inductance and resistance, while the impedance matching is achieved through on-die transmission line transformations.
Data Source
AI summary
An RF power amplifier includes an amplifier device and a shunt-inductance circuit. The amplifier device includes a substrate, a combining node lead, first and second amplifier dies coupled to the substrate, and first and second output circuits. The first and second amplifier dies are configured to amplify first and second input RF signals, respectively, to produce first and second output RF signals at first and second output terminals, respectively. The first output circuit includes a first inductive path connecting the first output terminal to the lead. The second output circuit includes a second inductive path connecting the second output terminal to the lead. The lead is configured to combine the first and second output RF signals to produce a third output RF signal. The shunt-inductance circuit is coupled between the first output terminal and a ground reference.