Current DAC Using Error Amplifiers to Reduce Die Size
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Solution Overview
Problem
Current digital-to-analog converters (DACs) face challenges with increased die size due to the need for cascoded current mirror branches and limited maximum drain-to-source voltage, which complicates their operation and minimization of die size in wireless terminals.
Innovation Solution
A current DAC design that eliminates the need for cascoded current mirror branches and increases the maximum drain-to-source voltage without increasing the width of current mirror FETs, utilizing a switchable resistor network and error amplifiers to equalize voltages and control current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cascoded current mirror branches are used to reduce variations in DAC output current, then output current stability is improved, but die size significantly increases
Solution Approach 1:
The patent introduces error amplifiers as intermediary components that detect voltage variations at the output node and generate corrective signals to compensate for these variations. This mediator approach stabilizes the output current without requiring cascoded transistor structures, thereby maintaining current stability while avoiding the significant die size increase that would result from cascoding all current mirror branches.
2Adaptability or versatility
If width of current mirror FETs is increased to increase maximum drain-to-source voltage, then maximum drain-to-source voltage is improved, but device dimensions increase
Solution Approach 1:
The patent implements feedback mechanisms where error amplifiers continuously monitor the output voltage and adjust the current mirror operation accordingly. This feedback control enables the system to maintain proper operation across a wider range of drain-to-source voltages without requiring increased FET width, thus achieving voltage adaptability while keeping device dimensions compact.
3Reliability
If voltage drop across FETs is increased to ensure proper operation, then operational reliability is improved, but output voltage range is reduced
Solution Approach 1:
Error amplifiers serve as intermediary components that enable the system to maintain reliable operation with smaller voltage drops across the FETs. By actively detecting and compensating for voltage variations, the error amplifiers allow the DAC to operate reliably across a broader output voltage range than would be possible with passive voltage drop requirements.
Data Source
AI summary
A current digital-to-analog converter (DAC) is disclosed. The current DAC includes a current reference circuit coupled between a voltage source terminal and a voltage node, wherein the current reference circuit includes a feedback node. A switchable resistor network is communicably coupled to the feedback node of the current reference circuit via a first feedback network that is adapted to equalize a first voltage across the switchable resistor network voltage with a second voltage between the feedback node and the voltage node. A current mirror includes an output node communicably coupled to the switchable resistor network via a second feedback network that is adapted to equalize an output current that flows from the output node with an input current that flows into the switchable resistor network.