Multi-Stage Power Amplifier Base Layout for Gain and Output
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Solution Overview
Problem
Power amplifiers for wireless communication, particularly in 5G systems, face challenges in increasing maximum output power and gain without complicating the fabrication process, as thinner base electrodes reduce parasitic resistance but also decrease gain due to increased base-collector junction capacitance.
Innovation Solution
A power amplifier design with multiple stages of bipolar transistors, where the base electrode width is adjusted to reduce parasitic resistance in the final stage and base-collector junction interface area in preceding stages, allowing for increased maximum output without compromising gain, without requiring complex fabrication processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the base electrode is made thinner to reduce the base-collector junction capacitance and increase gain, then the gain increases, but the parasitic resistance of the base electrode increases and the maximum output decreases
Solution Approach 1:
The patent applies local quality by making the base electrode width non-uniform across different regions. Specifically, the base electrode has a first width in the region overlapping the collector electrode and a second width in the region not overlapping the collector electrode, with the second width being greater than the first width. This allows different parts of the base electrode to have different functions: the narrower portion reduces base-collector junction capacitance for higher gain, while the wider portion reduces parasitic resistance for higher maximum output.
2Power
If the base electrode is made thinner to reduce the area of base-collector junction interface, then the base-collector junction capacitance decreases and gain increases, but the parasitic resistance increases
Solution Approach 1:
The patent applies local quality by making the base electrode width non-uniform across different regions. Specifically, the base electrode has a first width in the region overlapping the collector electrode and a second width in the region not overlapping the collector electrode, with the second width being greater than the first width. This allows different parts of the base electrode to have different functions: the narrower portion reduces base-collector junction capacitance for higher gain, while the wider portion reduces parasitic resistance for higher maximum output.
3Power
If the base layer and collector layer are removed to reduce base-collector junction interface area, then gain increases without decreasing maximum output, but the fabrication process becomes complicated and fabrication cost rises
Solution Approach 1:
The patent applies parameter changes by modifying the width parameter of the base electrode rather than removing entire layers. The base electrode width is changed from a uniform thin structure to a non-uniform structure with different widths in different regions. This parameter modification achieves the dual benefit of reduced base-collector junction capacitance and reduced parasitic resistance while maintaining the complete layer structure, thus avoiding complications in the fabrication process.
Data Source
AI summary
A power amplifier comprising amplifier circuits of multiple stages. Each of the amplifier circuits of multiple stages includes a bipolar transistor and a base electrode. The bipolar transistor included in each of the amplifier circuits of multiple stages includes a collector layer, a base layer placed on the collector layer, and an emitter mesa placed on part of the region of the base layer. The emitter mesa has a shape elongated in one direction in plan view. The base electrode includes a base main portion arranged in such a manner as to be separated from the emitter mesa with a gap in a direction orthogonal to a lengthwise direction of the emitter mesa in plan view. The base main portion has a shape elongated in a direction parallel to the lengthwise direction of the emitter mesa in plan view and is electrically connected to the base layer.