DAC Circuit Feedback Architecture for Low-Voltage Current Accuracy
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Solution Overview
Problem
The decreasing power supply voltage on semiconductor chips affects the accuracy of output current in digital-to-analog conversion circuits with current mirror structures, as the voltage headroom consumed by output transistors is insufficient, leading to inaccurate output current at the output resistor.
Innovation Solution
A digital-to-analog conversion circuit is designed with an operational amplification module and a conversion module, including a negative feedback circuit and a reference current module, where the operational amplification module includes transistors forming a current mirror with the reference transistors, and the conversion module uses resistors and switches to ensure proportional currents and voltages, allowing the circuit to operate with reduced voltage consumption while maintaining accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a current mirror structure is used in digital-to-analog conversion circuit, then conversion speed and matching accuracy are improved, but voltage headroom consumption increases, leading to insufficient voltage margin and reduced output current accuracy
Solution Approach 1:
The circuit is divided into two independent modules: a conversion module that performs digital-to-analog conversion and an operational amplification module that provides voltage feedback. This segmentation allows each module to operate independently with optimized voltage requirements, reducing the total voltage headroom consumption while maintaining conversion speed and accuracy.
Solution Approach 2:
The operational amplification module acts as an intermediary between the conversion module and the output resistor. It receives voltage feedback from the output and adjusts the conversion module's operation accordingly, enabling accurate output current control without requiring high voltage headroom in the current mirror structure itself.
2Speed
If output transistor is added to current mirror structure, then conversion speed is improved, but voltage headroom is consumed, affecting output current accuracy
Solution Approach 1:
A negative feedback circuit is implemented where the operational amplification module continuously monitors the output voltage and adjusts the conversion module's operation to maintain accurate output current. This feedback mechanism compensates for voltage headroom variations caused by the output transistor, preserving measurement precision while enabling fast conversion speed.
3Loss of energy
If power supply voltage is reduced, then energy consumption is decreased, but voltage headroom becomes insufficient, leading to inaccurate output current
Solution Approach 1:
The circuit changes its operating parameters dynamically through the operational amplification module. By adjusting the feedback voltage based on actual output conditions, the system can maintain accurate output current even at reduced power supply voltages, enabling low energy consumption without sacrificing measurement precision.
Data Source
AI summary
A digital-to-analog conversion circuit includes an operational amplification module having an operational amplifier connected to an output transistor to form a negative feedback circuit to obtain equal voltages at positive and negative ends. A negative end current flowing into the negative end is proportional to a positive end current flowing into the positive end. An input end of a conversion module is connected in parallel with a first resistor of the operational amplification module to obtain the same voltage as the first resistor, and an analog current proportional to the negative end current and positive end current. An output end of the conversion module is connected with the source of the output transistor and configured to receive the analog current and to make the analog current flow to an output resistor via the drain of the output transistor, to obtain an output current proportional to the positive end current.