Programmable Transconductance Resistor Network for Wider Input Range
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Solution Overview
Problem
Existing voltage-to-current converters, particularly those using R-2R resistor networks, are limited by the input range and common mode input range constraints, and require complex layouts and high output voltage ranges for achieving desired gain levels.
Innovation Solution
A transconductance stage combining a series resistor network for lower gains and an R-2R resistor network for higher gains, with additional switches to selectively connect nodes and short out resistors, reducing chip area and layout complexity while improving gain bandwidth and input range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If an R-2R resistor network is used for voltage-to-current conversion, then the converter can achieve compact layout, but the input range is limited by the amplifier output swing capability
Solution Approach 1:
The resistive network is divided into two portions: a first portion with series resistors for lower gains and a second portion with R-2R resistor network for higher gains. This segmentation allows each portion to operate in its optimal gain range, expanding the overall input range while maintaining compact layout benefits of the R-2R network.
2Adaptability or versatility
If a series resistor network is used for voltage-to-current conversion, then the input range can be expanded, but the number of resistors increases exponentially for a given number of binary steps
Solution Approach 1:
The resistive network is segmented into two portions: a first portion with series resistors for lower gains and a second portion with R-2R resistor network for higher gains. This segmentation allows each portion to operate in its optimal gain range, expanding the overall input range while maintaining compact layout benefits of the R-2R network.
Solution Approach 2:
The patent changes the gain parameter by selecting different portions of the resistive network. The first portion provides lower gains while the second portion provides higher gains, allowing the system to achieve a wide input range without requiring an exponentially large number of resistors.
3Power
If the resistive network is configured for higher gains, then the output current to input voltage ratio increases, but the output voltage range requirement increases
Solution Approach 1:
The resistive network is divided into two portions: a first portion with series resistors for lower gains and a second portion with R-2R resistor network for higher gains. This segmentation allows the system to achieve higher gains when needed while managing output voltage requirements through proper network configuration.
Data Source
AI summary
A voltage-to-current converter is provided. The voltage-to-current converter comprises an amplifier, a resistor network, an R-2R network, and switches. The amplifier has a first input node (which is an input signal), a second input node, and an output node. The resistor network is coupled to the output node of the amplifier, includes a plurality of resistors coupled in series with on another, and includes a plurality of first tap nodes. The R-2R network is coupled to the resistor network and includes a plurality of second tap nodes. Additionally, at least one switch is coupled between the second input node of the amplifier and each first tap node, and at least one switch is coupled between the second input node of the amplifier and each of the second tap nodes.