Analog Current Subtraction Circuit for Proximity Sensor Latency
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Solution Overview
Problem
Existing electronic devices with proximity sensors face latency and accuracy issues when performing signal subtraction in the digital domain.
Innovation Solution
Implementing a current subtraction circuit that computes the difference between current signals directly in the analog domain using a sample-and-hold circuitry, bias current source, current mirror circuitry, amplifier circuitry, and output current branch, allowing for precise calculation of signal differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If digital domain subtraction is used, then device complexity is reduced, but measurement precision and processing speed deteriorate
Solution Approach 1:
The patent replaces digital signal processing with an analog current-mode subtraction circuit. The circuit uses operational amplifiers configured in a differential configuration to directly subtract two current signals in the analog domain, eliminating the need for ADC conversion and digital processing. This substitution of analog for digital processing maintains high precision while reducing latency.
Solution Approach 2:
The patent introduces sample-and-hold circuitry as an intermediary component before the subtraction operation. This intermediary captures and holds the input current signals, ensuring accurate timing and preventing signal degradation during the subtraction process, thereby maintaining measurement precision in the analog domain.
2Ease of operation
If digital domain subtraction is used, then ease of operation is improved, but processing speed deteriorates due to latency
Solution Approach 1:
The patent replaces the multi-step digital processing chain (ADC conversion, digital subtraction, DAC conversion) with a single analog subtraction operation using operational amplifiers. This eliminates conversion latency and enables real-time processing, dramatically improving processing speed while maintaining operational simplicity through the inherent ease of analog circuit operation.
3Measurement precision
If analog current subtraction is implemented, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent employs operational amplifiers that perform multiple functions: they amplify the input signals, perform the subtraction operation, and provide impedance matching. This multi-functionality reduces the need for separate components, thereby limiting the increase in device complexity while achieving high measurement precision through accurate analog subtraction.
Solution Approach 2:
The patent utilizes the electrical parameters (current, voltage, impedance) of the operational amplifiers to achieve precise subtraction. By carefully selecting and adjusting these parameters, the circuit achieves high accuracy without requiring complex additional components, thus limiting complexity increase while improving measurement precision.
Data Source
AI summary
An electronic device may include a sensing circuit and a current subtraction circuit. The sensing circuit may output first and second current signals. The current subtraction circuit may mirror the first and second current signals onto first and second current branches. The second current branch may be split into a first sub-path and a second sub-path. An amplifier may control the amount of current flowing through the second sub-path by forcing the current flowing through the first current branch and the current flowing through the first sub-path to be identical. Configured in this way, the current flowing through the second sub-path will be equal to the difference between the first and second current signals. The current flowing through the second sub-path may be optionally amplified using another current mirror.