Floating-Voltage DAC Superposition Circuit for Precision Output
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Solution Overview
Problem
Existing superposition operation circuits face challenges in achieving high precision with low input signal precision requirements while maintaining low power consumption, particularly in voltage superposition, where the difference between digital and analog signals leads to nonlinear errors and inconsistencies.
Innovation Solution
A superposition operation circuit incorporating a current generation circuit and operational amplifiers, which converts voltage signals to current signals and uses a resistor to superpose the signals, ensuring the output work point is fixed at the to-be-superposed analog element, thereby improving precision and reducing input signal precision requirements without increasing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional operational amplifier is used to hold the virtual ground potential at the inverting input terminal, then the basic circuit function is achieved, but the input impedance becomes dependent on the operational amplifier's characteristics which limits adaptability
Solution Approach 1:
The patent introduces a dedicated impedance control circuit as an intermediary component between the signal source and the summing junction. This circuit includes a control circuit that generates impedance control signals and switching elements that adjust the impedance of impedance control circuits, thereby independently controlling input impedance without affecting the virtual ground holding function.
Solution Approach 2:
The patent segments the operational amplifier's input terminal into two functionally independent parts: the virtual ground holding function and the input impedance control function. By adding separate impedance control circuits connected to the inverting input terminal, each function can be controlled independently through separate control signals.
2Productivity
If multiple digital-to-analog conversion circuits are integrated on the same substrate to improve integration density, then productivity increases, but matching errors between circuits increase due to process variations
Solution Approach 1:
The patent employs trimming circuits that can adjust the resistance values of current mirror circuits and switching elements after fabrication. By changing the electrical parameters (resistance values) through trimming, the circuits can be compensated for process variations and achieve precise matching even when integrated on the same substrate.
Solution Approach 2:
The patent incorporates feedback mechanisms where the output of each digital-to-analog conversion circuit is monitored and used to adjust the trimming control signals. This feedback allows automatic compensation for matching errors caused by process variations, ensuring consistent performance across multiple integrated circuits.
3Measurement precision
If trimming control signals are applied to switching elements to correct output errors, then measurement precision improves, but the number of required control signals and circuit complexity increase
Solution Approach 1:
The patent designs trimming control circuits that can be universally applied to multiple switching elements within each digital-to-analog conversion circuit. A single trimming control signal can adjust multiple switching elements simultaneously, and the same trimming circuit structure is reused across all integrated digital-to-analog conversion circuits, reducing overall complexity.
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 ensures high-precision superposition with reduced power consumption and area requirements by converting low-absolute-precision voltage signals to high-precision current elements, addressing the limitations of existing circuits in achieving precise voltage superposition.
Implementation Method 1
MOS transistors controlled by each pair of inputs V + and V - of an operational amplifier may be equivalent to one voltage-controlled current source
Implementation Method 2
an output voltage is a voltage drop generated after a current generated by the controlled current source passes through a resistor
Data Source
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AI summary
This application provides a superposition operation circuit and a float-voltage digital-to-analog conversion circuit, to superpose analog elements according to an indirect current superposition principle. A voltage follower is implemented by using a first operational amplifier, so that an output end of the voltage follower is clamped to a voltage that is input to a positive-phase input end, namely, a to-be-superposed analog element. Then a current generation circuit converts a voltage signal to a current signal, a voltage drop for the current signal is generated on a first resistor connected to an output end of the first operational amplifier, and the voltage drop is superposed on a voltage signal output by the first operational amplifier. Because an output work point of the first operational amplifier in the superposition operation circuit is always fixed at the to-be-superposed analog element, output precision of the operational amplifier is ensured. In addition, because a high-precision superposed current element is obtained by converting a low-absolute-precision voltage signal, but is not directly generated by a digital-to-analog conversion circuit, an input precision requirement for the current generation circuit is lowered, and then requirements for power consumption and an area of the current generation circuit are lowered.