Voltage-to-Current Converter Linearity With Degeneration Resistors
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Solution Overview
Problem
Voltage-to-current converters in electronic devices introduce noise and nonlinearity into current-mode output signals, which can degrade transmit emissions and limit the performance of wireless communication systems.
Innovation Solution
The implementation of a voltage-to-current converter with strategically positioned degeneration resistors to redirect noise away from input transistors and biasing current-source transistors in the triode region to enhance linearity, reducing noise and nonlinearity in the output signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a voltage-to-current converter is used to convert voltage-mode signaling to current-mode signaling, then signal conversion is achieved, but noise and nonlinearity are injected into the current-mode output signal
Solution Approach 1:
The patent extracts and removes the harmful noise and nonlinearity components from the current-mode output signal by using a noise cancellation circuit that identifies and eliminates these unwanted elements while preserving the useful signal conversion function
Solution Approach 2:
The patent introduces an intermediary noise cancellation circuit between the voltage-to-current converter and the output that acts as a mediator to filter out noise and nonlinearity, allowing the signal conversion to proceed while the harmful factors are removed by this intermediate stage
2Object-generated harmful factors
If degeneration resistors are positioned between input transistor and current-source transistor, then noise is redirected away from input transistor, but device complexity increases
Solution Approach 1:
The patent applies local quality by strategically positioning degeneration resistors only in specific locations where they are most effective at redirecting noise away from the input transistor, rather than uniformly throughout the circuit, thus achieving noise reduction with minimal added complexity
Solution Approach 2:
The patent changes the electrical parameters of the circuit by introducing degeneration resistors that modify the noise characteristics and signal flow paths, transforming the noise behavior to achieve reduction while maintaining acceptable circuit simplicity
3Manufacturing precision
If current-source transistor is biased in triode region instead of saturation region, then linearity is improved, but current flow characteristics change
Solution Approach 1:
The patent changes the operating region parameter of the current-source transistor from saturation to triode region, which fundamentally alters the current-voltage characteristics to achieve improved linearity in the signal conversion process
Solution Approach 2:
The patent exploits the dynamic current flow characteristics of the triode region where current can be more easily modulated in response to input voltage changes, enhancing the linearity of the conversion while managing power consumption through this dynamic behavior
Data Source
AI summary
An apparatus is disclosed for voltage-to-current conversion. In example aspects, the apparatus has a voltage-to-current converter including a plus input transistor, a minus input transistor, a plus current-source transistor, a minus current-source transistor, a plus resistor, and a minus resistor. The plus current-source transistor is coupled between the plus input transistor and a power distribution node. The minus current-source transistor is coupled between the minus input transistor and the power distribution node. The plus resistor is coupled between the plus input transistor and the plus current-source transistor. The minus resistor is coupled between the minus input transistor and the minus current-source transistor.