Complementary Current-Steering DAC With TIA for Low-Noise Compact Output
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Solution Overview
Problem
Current digital-to-analog converters (DACs) face a trade-off between noise performance and circuit size, particularly in high-power applications where increased Error Vector Magnitude (EVM) and Radio Frequency (RF) impediments necessitate improved digital calibration, requiring a low-noise DAC with small circuit size and high power performance.
Innovation Solution
A complementary current-steering DAC design incorporating a transimpedance amplifier (TIA), p-type, and n-type current sources, where the connection of these sources to the TIA input terminals is dynamically switched based on digital input values to optimize current distribution and reduce circuit size while maintaining low noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional DAC design is used to achieve low noise performance, then the noise performance is improved, but the circuit size increases
Solution Approach 1:
The DAC is divided into two separate sub-DACs: a first current-steering DAC with first current sources and a second current-steering DAC with second current sources. Each sub-DAC handles a portion of the digital input bits, allowing independent optimization of each segment. This segmentation enables reduced circuit size while maintaining overall noise performance through coordinated operation of both segments.
Solution Approach 2:
The output currents from the first and second current-steering DACs are merged through a summing node to produce the final analog output. This merging approach combines the benefits of both sub-DACs, achieving low noise performance through current summation while keeping individual circuit segments compact and efficient.
2Reliability
If digital calibration is increased to address EVM and RF impediments, then the power performance is improved, but the circuit complexity increases
Solution Approach 1:
The DAC employs dynamic current steering where current sources are selectively activated based on digital input values. The switching mechanism dynamically connects or disconnects current sources from the summing node, enabling flexible power management and calibration without requiring complex static circuit structures. This dynamic operation achieves high power performance while maintaining relatively simple circuit architecture.
Solution Approach 2:
The DAC achieves power optimization by changing the operational parameters of current sources based on input conditions. Different current source configurations are activated depending on the digital input pattern, allowing the circuit to adapt its power consumption and performance characteristics without requiring complex additional calibration circuits.
Data Source
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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.