Pre-Amplifier Tracking Circuit for Stable Common-Mode Output
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Pre-amplifier circuits in comparator circuits face instability in output common mode voltage when the input common mode voltage varies over a wide range, making it difficult to design subsequent stages and often requiring time-consuming and expensive stability analysis, along with introducing undesirable elements in the differential signal path.
Innovation Solution
A tracking circuit is coupled with the pre-amplifier circuit to provide an additional current through an alternate current path when the input common mode is beyond a saturation range, using a scaling factor and mirroring ratio to stabilize the output common mode voltage, and this is achieved by creating a scaled version of input transistors in the tracking circuit and adding the additional current through a common mode resistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a negative feedback loop is used to stabilize output common mode voltage, then the output common mode voltage stability is improved, but the design complexity and time consumption increase due to required stability analysis
Solution Approach 1:
A tracking circuit is introduced as an intermediary component that mirrors the input common mode voltage and provides compensating current to stabilize the output common mode voltage. This mediator approach avoids the complexity of negative feedback stability analysis while achieving the desired voltage stability through current mirroring and compensation.
Solution Approach 2:
The tracking circuit implements a form of feedback by continuously monitoring the input common mode voltage and adjusting the compensating current accordingly. This active feedback mechanism stabilizes the output common mode voltage without requiring traditional negative feedback loop stability analysis.
2Stability of the object's composition
If a negative feedback loop is used to stabilize output common mode voltage, then the output common mode voltage stability is improved, but time consumption increases due to stability analysis requirements
Solution Approach 1:
The tracking circuit serves as a mediator that directly stabilizes the output common mode voltage through current mirroring, eliminating the need for time-consuming stability analysis associated with traditional negative feedback loops. This approach significantly reduces design time while maintaining voltage stability.
3Adaptability or versatility
If the input common mode varies over a wide range, then the adaptability of the pre-amplifier circuit is improved, but the output common mode voltage becomes unstable
Solution Approach 1:
The tracking circuit acts as an intermediary that compensates for wide variations in input common mode voltage by providing appropriate compensating current. This allows the pre-amplifier circuit to maintain adaptability across a wide input range while the tracking circuit ensures output common mode voltage stability through active compensation.
Solution Approach 2:
The tracking circuit dynamically adjusts the compensating current parameter in response to changes in input common mode voltage. By changing this current parameter based on the input voltage level, the circuit maintains stable output common mode voltage across a wide adaptability range.
4Stability of the object's composition
If correction circuits are added to stabilize output common mode voltage, then the output common mode voltage stability is improved, but undesirable elements are introduced in the differential signal path
Solution Approach 1:
The correction function is segmented into a separate tracking circuit that operates independently from the main differential signal path. This segmentation allows the stabilization function to be added without introducing undesirable elements into the critical differential signal path, as the tracking circuit handles compensation through a separate current mirroring mechanism.
Data Source
AI summary
A method, apparatus and system of constant output common mode voltage of a pre-amplifier circuit are disclosed. In one embodiment, a system includes a first circuit, a comparator circuit coupled with an output of the first circuit, a pre-amplifier circuit of the comparator circuit, a tracking circuit coupled with a common output location of the pre-amplifier circuit to provide (e.g., source/sink) an additional current to the common output location of the pre-amplifier circuit using an alternate current path in the tracking circuit when an input common mode of the pre-amplifier circuit is beyond a saturation range, and a second circuit of the comparator circuit coupled with the pre-amplifier circuit. A scaled version of a pair of input transistors of a pre-amplifier circuit of the tracking circuit may be created using a scaling factor (‘N’).