Differential Doherty Amplifier Layout for Low-Inductance RF Output
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Solution Overview
Problem
The output characteristics of Doherty amplifiers degrade due to layout issues on printed circuit boards, particularly with high-frequency radio-frequency signals, making it difficult to suppress inductance values and maintain symmetry in wiring configurations.
Innovation Solution
The Doherty amplifier design incorporates differential amplifiers with phase shifters and baluns, where some wiring is formed on the integrated circuit and others on the printed wiring board, minimizing detours and reducing inductance values by direct connections through bumps and vias, ensuring symmetry and reducing inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If all wirings are formed on the printed wiring board, then ease of manufacture is improved, but inductance values increase and output characteristics degrade
Solution Approach 1:
The wiring path is segmented into two parts: one wiring is formed on the printed wiring board while the other wiring is formed on the integrated circuit substrate. This segmentation allows each part to be optimized for its specific function, reducing overall inductance while maintaining manufacturing feasibility.
Solution Approach 2:
The solution moves from a two-dimensional planar wiring layout on the PCB to a three-dimensional configuration where wirings exist on different substrates (PCB and IC). This dimensional change enables direct connection through bumps and vias, minimizing detour paths and reducing inductance.
2Ease of operation
If wiring detours are increased to connect output terminals, then ease of connection is improved, but inductance values increase
Solution Approach 1:
By utilizing the vertical dimension through bumps and vias, the wiring path is shortened significantly. The direct connection through the substrate thickness is much shorter than any possible detour on the surface, thereby reducing inductance while maintaining connectivity.
3Ease of manufacture
If wiring symmetry is compromised for layout flexibility, then ease of manufacture is improved, but output characteristics degrade
Solution Approach 1:
The patent intentionally creates asymmetric wiring paths: one wiring on the PCB and another on the IC substrate. This controlled asymmetry allows each wiring to be positioned optimally for its function while maintaining overall system symmetry in terms of electrical characteristics and performance.
Data Source
AI summary
A Doherty amplifier includes a carrier amplifier and a peak amplifier. Each of the carrier amplifier and the peak amplifier is a differential amplifier including a first phase amplifier and a second phase amplifier. The Doherty amplifier also includes a balun configured to synthesize an output signal of the carrier amplifier and an output signal of the peak amplifier. The carrier amplifier and the peak amplifier are formed in an integrated circuit. The balun is formed on a printed wiring board on which the integrated circuit is mounted.