Multi-Stage Differential Amplifier With Common-Mode Node Shorting
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Solution Overview
Problem
Conventional multi-stage amplifiers face issues with large common-mode disturbances due to inadequate gain and inefficient common-mode termination techniques, leading to nonlinear distortion and performance degradation, often requiring large capacitors or power-hungry buffers.
Innovation Solution
A multi-stage amplifier design that connects single-stage differential amplifiers in a cascade arrangement with a shorting path between common-mode nodes, allowing for small or omitted capacitive termination and eliminating the need for power-hungry buffers, thereby suppressing common-mode gain efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a large-sized common-mode termination capacitor is used, then common-mode disturbance is reduced, but area consumption increases
Solution Approach 1:
The patent merges the common-mode termination function with the existing output network by shorting the common-mode nodes of multiple stages together. This eliminates the need for separate large termination capacitors at each stage, achieving common-mode suppression without additional area consumption.
Solution Approach 2:
The patent extracts the common-mode termination function from the traditional capacitor-based implementation and relocates it to the common-mode node shorting path. This separation allows the termination function to be achieved through the existing amplifier stages rather than requiring additional large capacitive elements.
2Object-affected harmful factors
If a power-hungry operation amplifier buffer with very low impedance is used for common-mode termination, then common-mode disturbance is reduced, but power consumption increases
Solution Approach 1:
The patent implements self-service by using the existing amplifier stages to provide common-mode suppression through their inherent gain characteristics. The amplifiers serve dual purposes: signal amplification and common-mode termination, eliminating the need for separate power-hungry buffer amplifiers.
Solution Approach 2:
The patent combines the common-mode termination function with the signal amplification function in the same amplifier stages. By shorting the common-mode nodes, the existing amplifier circuits perform both functions simultaneously, removing the need for additional power-consuming buffer stages.
3Power
If multiple amplifier stages are connected in cascade to increase gain, then amplification capability is improved, but common-mode disturbances increase
Solution Approach 1:
The patent applies feedback by using the negative common-mode gain of subsequent stages to suppress common-mode signals from previous stages. The shorted common-mode nodes create a feedback mechanism where later stages actively cancel common-mode disturbances from earlier stages, allowing cascade connection without accumulating common-mode errors.
Data Source
AI summary
A multi-stage amplifier includes a plurality of single-stage differential amplifiers that are connected in a cascade arrangement. The single-stage differential amplifiers include a first single-stage differential amplifier and a second single-stage differential amplifier. The first single-stage differential amplifier has a first output network. The second single-stage differential amplifier has a second output network. A common-mode (CM) node of the second output network is shorted to a CM node of the first output network.