CMOS Distributed Amplifier with Common-Mode Feedback Biasing
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Solution Overview
Problem
Existing distributed amplifiers (DAs) in RF communication systems face challenges in achieving low power consumption, low noise, and high power gain due to the need for external bias circuits and poor linearity, which limits their integration on a single semiconductor chip.
Innovation Solution
A CMOS distributed amplifier design utilizing multi-stage Gm cells with common mode feedback and negative resistance, eliminating the need for output drain bias and enhancing DC gain, implemented with CMOS inverter-based Gm cells for efficient signal transmission and amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a prior art distributed amplifier uses a simple NMOS common source inverter structure with external bias circuits, then the circuit can be implemented, but the noise figure increases and linearity deteriorates
Solution Approach 1:
The patent merges the bias circuit functionality into the Gm cell structure itself. The common mode feedback circuit is integrated within each Gm cell, eliminating the need for separate external bias circuits. This integration reduces the noise figure and improves linearity while maintaining ease of manufacture through standardized cell design.
Solution Approach 2:
The patent introduces common mode feedback within each Gm cell to control and stabilize the operating point. This feedback mechanism improves linearity by compensating for non-linearities in the transistor operation and reduces noise figure by maintaining optimal bias conditions across the distributed amplifier stages.
2Ease of manufacture
If a distributed amplifier uses external bias circuits and matching circuits, then the amplifier can be implemented, but the device complexity increases
Solution Approach 1:
The patent combines multiple functions (biasing, matching, and amplification) into the integrated Gm cell structure. The common mode feedback circuit is embedded within each cell, eliminating the need for separate external bias circuits and matching networks, thereby reducing device complexity while maintaining implementability.
Solution Approach 2:
The Gm cell structure is designed to perform multiple functions simultaneously: signal amplification through transconductance, biasing through integrated common mode feedback, and impedance matching. This multi-functionality reduces the number of discrete components needed and simplifies the overall amplifier design.
3Productivity
If a distributed amplifier is designed for wide bandwidth and high gain, then the amplifier performance improves, but the power consumption increases
Solution Approach 1:
The patent divides the distributed amplifier into multiple identical Gm cell stages connected in cascade. Each cell operates at a lower individual power consumption level, but the cumulative effect across multiple stages achieves the desired wide bandwidth and high gain. The segmentation allows for optimized power distribution across stages.
Solution Approach 2:
The patent optimizes the transconductance parameter (Gm) of each cell to achieve the desired bandwidth and gain performance while minimizing power consumption. By carefully selecting and matching the Gm values across stages, the amplifier achieves high productivity with reduced energy usage compared to conventional designs.
Data Source
AI summary
Provided is a distributed amplifier in communication systems, including: an input transmission line; an output transmission line; an input impedance match and an output impedance match, for providing termination of the input transmission line and the output transmission line, respectively and for preventing signal reflection in the input transmission line and the output transmission line, respectively; multi-stage Gm cells with common mode feedback, the input transmission line being coupled to the output transmission line by the transconductance of the Gm cells; and an input gate bias circuit, for providing bias for the multi-stage Gm cells. In at least one of the Gm cells, one inverter performs V/I conversion while other inverters provide negative resistance to control common mode of output voltage and to enhance DC gain of the Gm cell. Due to common mode feedback, no output gate bias is needed.