Current-Mirror DAC Circuit for Early-Effect Linearity Control
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Solution Overview
Problem
The linearity of digital/analog conversion in existing DACs deteriorates due to the Early effect, causing fluctuations in potential at the output point, which worsens the balance of digit weightings and affects the accuracy of current output.
Innovation Solution
A digital/analog conversion circuit is designed with a second and third current mirror circuit connected to a reference voltage, generating mirror currents that stabilize the potential at the output point, ensuring the voltage remains constant regardless of changes in input digital codes, thereby suppressing the Early effect and improving linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current mirror circuit is used to generate output current according to input digital code, then the DAC can convert digital signals to analog current, but the potential at the output point fluctuates due to the Early effect, causing deterioration of linearity
Solution Approach 1:
The patent introduces a third current mirror circuit as an intermediary between the first current mirror circuit and the digital/analog conversion portion. This intermediary circuit, connected to a reference voltage terminal, stabilizes the potential at the output point by providing a constant voltage reference, thereby preventing the Early effect from causing potential fluctuations and linearity deterioration.
2Measurement precision
If the potential at the output point fluctuates, then the digit weightings balance is worsened, but adding stabilization circuits increases circuit complexity
Solution Approach 1:
The third current mirror circuit serves multiple functions simultaneously: it acts as a current mirror to generate mirror current, provides voltage stabilization at the output point, and references the reference voltage terminal. This multi-functionality allows the circuit to improve digit weighting balance without proportionally increasing complexity, as the stabilization function is integrated into the existing current mirror architecture.
Data Source
AI summary
In an mode of this invention, a digital/analog conversion circuit, includes: a digital/analog conversion portion which outputs a first current according to an input digital signal; and a first current mirror circuit which generates a mirror current according to the first current and outputs the mirror current as an analog signal, the digital/analog conversion circuit converting the digital signal into the analog signal, and further including: a second current mirror circuit, which generates a first mirror current according to the first current; and a third current mirror circuit, which is connected to a reference voltage, and to which the first mirror current is input, and which generates a second mirror current equal to the first current, according to the first mirror current, between the digital/analog conversion portion and the second current mirror circuit.