Complementary Current-Steering DAC With Fewer Current Sources
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Solution Overview
Problem
Existing digital-to-analog converters (DACs) face challenges in achieving low-noise performance with small circuit size and high power efficiency, particularly in meeting increased Error Vector Magnitude (EVM) requirements due to technological advancements in wireless communication.
Innovation Solution
A complementary current-steering DAC is introduced, comprising a p-type DAC and an n-type DAC, with flexible bias current switching to reduce the number of current sources and circuit size, utilizing a transimpedance amplifier (TIA) to manage input terminals based on digital input changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional DAC design is used, then the circuit can achieve basic digital-to-analog conversion, but the circuit size and power consumption are excessive while noise performance is insufficient
Solution Approach 1:
The DAC is divided into two independent sub-DACs: a p-type DAC with p-type current sources and an n-type DAC with n-type current sources. Each sub-DAC handles half of the digital input bits, allowing parallel operation with reduced circuit size while maintaining low noise performance through complementary current steering.
Solution Approach 2:
The p-type and n-type DACs are merged into a single complementary current-steering DAC structure that shares common current sources and switching mechanisms. This integration reduces overall circuit area while the complementary design maintains low noise through balanced current paths.
2Measurement precision
If more current sources are used to improve resolution, then the DAC precision increases, but the circuit size and power consumption increase
Solution Approach 1:
The total number of current sources is segmented between two sub-DACs. Each sub-DAC uses fewer current sources than a conventional single DAC would require for the same resolution, reducing the total quantity while maintaining precision through parallel operation.
Solution Approach 2:
The design changes the operational parameters by using complementary p-type and n-type current sources that can operate in parallel. This allows the DAC to achieve high resolution with fewer total current sources by utilizing both positive and negative type carriers simultaneously.
Data Source
AI summary
A complementary current-steering digital-to-analog converter (DAC) including a p-type DAC as well as an n-type DAC is shown. The p-type DAC has p-type current sources, and the n-type DAC has n-type current sources. The p-type and n-type current sources are coupled to a first input terminal or a second input terminal of a transimpedance amplifier (TIA) according to the digital input of the complementary current-steering DAC. In response to the digital input changing from a first value to a second value that is greater than the first value, one or more n-type current sources connected to the second input terminal of the TIA are switched so that they are connected to the first input terminal of the TIA.