Differential-to-Single-Ended Comparator Circuit With Feedthrough Isolation
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Solution Overview
Problem
Conventional multi-stage comparators face limitations due to the phenomenon of feedthrough by reset switches in the conversion from differential to single-ended signals, leading to performance and reliability issues.
Innovation Solution
A circuit design that includes buffer circuits to equalize the output impedances of the single-ended circuit, using additional capacitors and switches to minimize the difference in feedthrough charges across decoupling capacitors, thereby reducing the impact of feedthrough and enhancing the comparator's speed and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reset switches are used in the single-ended operational element for conversion from differential to single-ended signals, then the comparator can be reset to reach the best bias condition and store offset voltages in decoupling capacitors, but feedthrough phenomenon occurs causing performance and reliability limitations
Solution Approach 1:
The patent introduces buffer circuits as intermediary elements between the single-ended operational element and the decoupling capacitors. These buffer circuits act as mediators that isolate the feedthrough effect from the capacitors while maintaining the reset functionality, thereby eliminating the harmful feedthrough phenomenon without sacrificing the ability to store offset voltages.
Solution Approach 2:
The patent extracts the harmful feedthrough effect from the signal path by removing the direct connection between the reset switches and the decoupling capacitors. The buffer circuits are positioned to take out the feedthrough charges before they can affect the capacitor voltages, separating the useful reset function from the harmful feedthrough effect.
2Productivity
If conventional single-ended operational elements are used with reset switches, then the circuit can perform differential to single-ended conversion, but the difference in feedthrough charges across decoupling capacitors reduces performance
Solution Approach 1:
Buffer circuits are introduced as intermediary stages that prevent direct coupling between the reset switches and the decoupling capacitors. This intermediary structure maintains the conversion efficiency while eliminating the precision-degrading feedthrough effect, as the buffers isolate the capacitor voltages from switch-induced charge injection.
3Duration of action of moving object
If reset switches are directly connected to decoupling capacitors in the single-ended stage, then the operational element can be reset and offset stored, but the feedthrough effect reduces speed and reliability
Solution Approach 1:
The buffer circuits serve as intermediary stages that enable the reset operation to complete without the speed-penalty feedthrough effect. The buffers allow the reset switches to charge/discharge the capacitors at their natural pace while preventing feedthrough charges from corrupting the signal, thus maintaining both the required reset duration and high operating speed.
Data Source
AI summary
An electrical circuit for conversion from differential to single-ended includes a differential amplifier stage and first and second buffer circuits. The differential amplifier stage includes a first and a second input; and a first and a different second charging circuit that can be operatively coupled, respectively, with an output of the conversion circuit and with an auxiliary output. Each of the first and second buffer circuits is functionally arranged between one of said outputs and between one of said charging circuits. The buffer circuits being configured so as to substantially equalize relative impedances seen towards said outputs.