Current Switch Circuit With Substrate Bias for Wider DAC Output Range
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Solution Overview
Problem
Conventional current switch circuits for D/A converters face challenges in achieving a wide output voltage range while maintaining low power consumption and chip area efficiency, especially with low power voltage operations, and are sensitive to threshold voltage variations due to production processes.
Innovation Solution
A current switch circuit with a threshold voltage control circuit that adjusts the substrate voltage of transistors in the differential switch to achieve a higher threshold voltage, allowing for a wider output voltage range without increasing power consumption or chip area, and maintaining stability against threshold voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If low power voltage is used to reduce power consumption, then power consumption is reduced, but the output voltage range becomes narrow
Solution Approach 1:
The patent changes the threshold voltage parameter of the differential switch transistors to a higher value (e.g., 0.7V) while maintaining low power supply voltage (1.8V). This parameter change allows the output voltage range to extend beyond the threshold voltage limitation, achieving wider output range without increasing power consumption. The higher threshold voltage is achieved through substrate biasing or transistor design modifications.
2Length of moving object
If threshold voltage of differential switch transistors is increased to widen output voltage range, then output voltage range is widened, but sensitivity to production process variations increases
Solution Approach 1:
The patent introduces a feedback mechanism where the threshold voltage of the differential switch transistors is dynamically adjusted based on detected threshold voltage variations. A threshold voltage detection circuit monitors the actual threshold voltage, and a control circuit modifies the substrate bias or gate voltage to compensate for deviations, thereby maintaining stable output characteristics despite production process variations.
3Use of energy by stationary object
If conventional current switch circuit is used with low power voltage, then power consumption is reduced, but the output voltage range is limited by threshold voltage
Solution Approach 1:
The patent makes the threshold voltage dynamic rather than fixed by introducing substrate biasing control. The substrate voltage is adjusted dynamically to optimize the threshold voltage according to operating conditions, allowing the circuit to maintain low power consumption while adapting the output voltage range to meet system requirements. This dynamic adjustment enables the circuit to overcome the static threshold voltage limitation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables a wider output voltage range without deteriorating circuit properties, reduces chip area and power consumption, and maintains a constant output voltage range despite production process variations, effectively addressing the limitations of conventional designs.
Implementation Method 1
a threshold voltage control circuit for outputting a substrate voltage to a substrate terminal of each of the first and second transistors to adjust a threshold voltage of the first and second transistors
Data Source
AI summary
[Means for Solving the Problem] In a current switch circuit A used for a current steering D/A converter, a current switch basic circuit 1 includes first and second transistors Tr121 and Tr122 included in a differential switch 12. A threshold voltage control circuit 5 has an output terminal Vbout controlling the substrate voltage to be outputted to the substrate terminal of each of the two transistors Tr121 and Tr122 included in the differential switch 12 for controlling the threshold voltage of the two transistors of the differential switch. Accordingly, the present invention improves the decrease in the dynamic range of the current switch basic circuit 1 dependent on the threshold of each of the two transistors in the differential switch 12 and realizes a wider output voltage range without causing deterioration in properties even in a case that the power voltage is reduced in the current switch basic circuit 1.