RF Transistor Packages with Segmented Matching Networks
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Packaged RF transistors face stability issues due to the creation of lower frequency feedback paths between adjacent cells caused by single capacitors in internal matching networks, which can reduce the overall device stability and lead to odd mode oscillations.
Innovation Solution
The use of multiple parallel capacitors in internal matching networks, with wirebond connections to respective cells of a multi-cell RF transistor die, and separate capacitors for each transistor cell in the output matching network, along with conductive or resistive connectors to reduce resonance modes and improve stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single capacitor is used in the internal matching network, then the device structure is simple, but lower frequency feedback paths are created between adjacent cells causing stability issues and odd mode oscillations
Solution Approach 1:
The single capacitor is segmented into multiple capacitors (first capacitor and second capacitor) that are respectively coupled to adjacent transistor cells. This segmentation eliminates the common feedback path that caused low-frequency oscillations, as each capacitor is now isolated to serve specific cells rather than creating a shared feedback loop between adjacent cells.
2Reliability
If multiple capacitors are used in the output matching network, then stability is improved by reducing feedback paths, but device complexity increases
Solution Approach 1:
Different capacitor configurations are applied to different regions of the device. The first capacitor is coupled to first transistor cells while the second capacitor is coupled to second transistor cells, creating localized matching networks that are optimized for specific cell groups. This local quality approach improves stability without requiring complete redesign of the entire matching network.
Data Source
Figure 1~2B
Figure 3
Figure 4~5
AI summary
A packaged RF transistor device includes an RF transistor die including a plurality of RF transistor cells, an RF input lead coupled to the plurality of RF transistor cells, an RF output lead, and an output matching network coupled between the plurality of RF transistor cells and the RF output lead. The output matching network includes a plurality of capacitors having respective upper capacitor plates, wherein the upper capacitor plates of the capacitors are coupled to output terminals of respective ones of the RF transistor cells. The plurality of capacitors may be provided as a capacitor block that includes a common reference capacitor plate and a dielectric layer on the reference capacitor plate. The upper capacitor plates may be on the dielectric layer.