Voltage-to-Current Converter Switching for Compact Current Accuracy
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Solution Overview
Problem
Voltage-to-current converters face challenges in reducing size while maintaining performance and accuracy, particularly due to transistor mismatch and variations in electrical characteristics during fabrication, leading to accuracy drops in output current.
Innovation Solution
The design incorporates a voltage-to-current converter with a first and second transistor, an operational amplifier, control circuit, and resistors, where the control circuit adjusts the equivalent resistance by switching between transistors and resistors to maintain accurate output current, and a determination circuit or operational amplifier with multiple input terminals to average voltages and mitigate mismatch effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If transistors/switches are made smaller to reduce converter size, then the size of the voltage-to-current converter is reduced, but it becomes difficult to meet resistance specification requirements
Solution Approach 1:
The patent divides the current path into multiple segments by introducing multiple transistors (first transistor, second transistor) and multiple resistors (first resistor, second resistor). This segmentation allows each component to be optimized independently, enabling smaller transistor sizes while maintaining overall resistance specifications through the combined effect of multiple segments.
Solution Approach 2:
The patent changes the resistance parameter by dynamically switching between different transistor-resistor combinations. The control circuit adjusts which transistors are active and which resistors are connected, thereby changing the equivalent resistance to meet specification requirements even when individual transistors are smaller than traditional designs.
2Volume of moving object
If transistors/switches are made smaller, then the converter size is reduced, but fabrication variations cause transistor mismatch and accuracy degradation
Solution Approach 1:
The patent introduces resistors with matched resistance values to compensate for transistor mismatch. By ensuring that the resistors have homogeneous (matched) resistance characteristics, the circuit achieves balanced current distribution even when transistors exhibit fabrication variations, thereby maintaining output current accuracy.
Solution Approach 2:
The control circuit monitors the output current and adjusts the switching states of transistors and resistors to maintain accurate output. This feedback mechanism compensates for mismatch effects by dynamically adjusting the circuit configuration to counteract fabrication variations.
3Measurement precision
If multiple transistors and resistors are added to compensate for mismatch, then accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges the functions of multiple transistors and resistors into a unified current generation structure. The first and second transistors work together with their corresponding resistors to produce the output current, combining multiple components into a single functional unit that achieves accuracy compensation without requiring separate compensation circuits.
Solution Approach 2:
The control circuit serves multiple functions: it controls the switching of transistors, manages the connection of resistors, and maintains output current accuracy. This multi-functional approach reduces the need for separate dedicated circuits for each function, thereby limiting the increase in overall device complexity.
Data Source
AI summary
A voltage-to-current converter includes a first transistor having a drain coupled to a first node, a second transistor having a drain coupled to the first node, an operational amplifier having a first input terminal configured to receive a reference voltage and a second input terminal coupled to a source of the first transistor or a source of the second transistor, a control circuit having an input terminal coupled to an output terminal of the operational amplifier, a first output terminal coupled to a gate of the first transistor, and a second output terminal coupled to a gate of the second transistor, a first resistor coupled between the source of the first transistor and a ground, and a second resistor coupled between the source of the second transistor and the ground. An output current of the voltage-to-current converter is generated from the first node.