Voltage-to-Current Converter Linearity via Segmented Sensing
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Solution Overview
Problem
Current voltage to current converters in circuit designs suffer from poor linearity performance due to the dual roles of devices in sensing input signals and carrying output signals, leading to limitations in signal resolution and increased distortion in high dynamic range applications, particularly in Sigma Delta Analog-to-Digital Converters and radio frequency/wireless applications.
Innovation Solution
The solution involves separating the sensing function and output current function into two distinct sets of devices, using a negative feedback loop and high-linearity resistors to convert input voltage signals to output current signals, with a common mode feedback loop regulating output common mode voltage to a reference voltage, thereby improving linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If devices are used for both sensing input voltage signal and carrying output current, then device functionality is integrated, but linearity performance deteriorates
Solution Approach 1:
The patent divides the device into two separate sets: a first set of devices dedicated to sensing the input voltage signal and a second set of devices dedicated to carrying the output current. This segmentation eliminates the conflict between sensing and current-carrying functions, allowing each set to optimize its specific function without compromising linearity performance.
Solution Approach 2:
The patent extracts the sensing function from the current-carrying function by removing the input signal sensing role from the output current path devices. The first set of sensing devices is taken out and separated from the second set of output devices, eliminating the non-linearity caused by dual-function devices.
2Productivity
If voltage to current converters are used to increase clock frequency for better quantization noise performance, then signal resolution may improve, but distortion increases due to poor linearity
Solution Approach 1:
By segmenting the converter into dedicated sensing devices and dedicated output devices, the patent enables high-speed operation at increased clock frequencies while maintaining linearity. The sensing devices can operate at high frequencies without introducing distortion, as they are not burdened with current-carrying responsibilities.
Solution Approach 2:
The patent implements a negative feedback loop that includes the first sensing device, the second output device, and an amplifier. This feedback mechanism compensates for any non-linearities and ensures that the converter maintains high linearity performance even at increased clock frequencies, preventing distortion from becoming the dominant factor.
3Speed
If filters operate at high frequencies to filter out blockers and images, then filtering capability improves, but distortion introduced by poor linearity overwhelms the benefit
Solution Approach 1:
The patent's segmented architecture with dedicated sensing and output devices enables the filter to operate at high frequencies required for blocking RF interferers and images. The separation ensures that high-frequency operation does not compromise linearity, allowing the filter to effectively remove blockers and images without introducing overwhelming distortion.
Data Source
AI summary
A system and method for performing voltage to current conversion, the system comprising of a first set of devices that senses the input voltage signal through its input terminal and replicates said input voltage across a second set of devices which then converts said replicated input voltage signal to an output current signal; a third set of devices that transfers the output current signal to output terminals; a differential feedback loop comprising an amplifier positioned between a first one of the first set of devices and a first one of the third set of devices; and a common mode feedback loop that regulates the output average voltage to a reference voltage.