Common-Mode Feedback Amplifier for Stable ADC Output Voltage
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Solution Overview
Problem
Existing signal amplifiers struggle to stabilize the output common mode voltage and improve the common mode rejection ratio, which affects their performance.
Innovation Solution
A signal amplifying circuit with a common mode feedback circuit that includes an output common mode voltage detection circuit, a pull-up circuit, and a pull-down circuit to control the output common mode voltage to a reference value, ensuring stability and improved common mode rejection ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a common mode feedback circuit is implemented to stabilize the output common mode voltage, then the common mode rejection ratio is improved, but the device complexity increases
Solution Approach 1:
The patent implements a common mode feedback circuit that detects the output common mode voltage and adjusts the common mode voltage through feedback control. The detection circuit monitors the common mode voltage level and generates control signals to regulate the common mode voltage, thereby improving the common mode rejection ratio while maintaining circuit stability.
Solution Approach 2:
The patent introduces an intermediate common mode voltage detection circuit and control circuit that act as mediators between the differential amplifier outputs and the common mode voltage regulation mechanism. This intermediary structure enables precise control of the common mode voltage without directly complicating the core differential amplification path.
2Stability of the object's composition
If the output common mode voltage is stabilized to a reference value, then the differential voltage swing is maximized, but the control circuit complexity increases
Solution Approach 1:
The patent stabilizes the output common mode voltage to a reference voltage level, creating an equipotential condition for the common mode voltage. This ensures that the common mode voltage remains constant at the desired reference level (typically the average of high and low operating voltages), maximizing the differential voltage swing capability of the amplifier.
Solution Approach 2:
The common mode feedback circuit automatically detects and corrects common mode voltage deviations without external intervention. The detection circuit continuously monitors the common mode voltage and the control circuit automatically adjusts it to maintain stability, enabling the system to self-regulate the common mode voltage level.
Data Source
AI summary
A signal amplifying circuit includes an amplifier and a common mode feedback circuit. The amplifier generates first and second outputs. The common mode feedback circuit receives the first and second outputs, and controls an output common mode voltage of the first and second outputs to a first reference voltage. The common mode feedback circuit includes an output common mode voltage detection circuit, a pull-up circuit and a pull-down circuit. The output common mode voltage detection circuit generates first and second control signals according to the output common mode voltage. The pull-up circuit with a first conduction degree controlled by the first control signal controls the output common mode voltage to be positively correlated with the first conduction degree. The pull-down circuit with a second conduction degree controlled by the second control signal controls the output common mode voltage to be negatively correlated with the second conduction degree.