Negative Voltage Comparison Circuit for Oxide Semiconductor Threshold Control
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Solution Overview
Problem
Current semiconductor devices face challenges in accurately generating negative voltages and controlling power consumption, particularly in devices using oxide semiconductor transistors where reliable threshold voltage control is lacking.
Innovation Solution
A comparison circuit is developed that directly inputs a negative voltage for comparison, utilizing a differential input circuit with n-channel transistors having backgates, which includes a latch circuit and a step-down charge pump circuit to generate high-accuracy negative voltages while reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a negative voltage output from a charge pump circuit is converted into a positive voltage for comparison, then the comparison can be performed using conventional comparator circuits, but the circuit complexity increases and power consumption increases due to the additional voltage conversion stage
Solution Approach 1:
Instead of converting the negative voltage to positive for comparison, the invention inverts the approach by designing a comparator circuit that directly compares negative voltages. The differential input circuit is configured to accept negative voltage inputs at the gates of n-channel transistors, eliminating the need for voltage conversion and reducing circuit complexity while maintaining comparison accuracy.
Solution Approach 2:
The invention extracts and removes the unnecessary voltage conversion stage from the conventional comparator circuit. By taking out the DC-DC converter component that was used to convert negative voltage to positive voltage, the circuit becomes simpler and consumes less power while still achieving reliable negative voltage comparison through the specialized differential input structure.
2Reliability
If a charge pump circuit is used to generate negative voltages, then negative potentials can be obtained, but the power consumption increases and the generation accuracy is difficult to control
Solution Approach 1:
The invention implements a feedback mechanism where the comparator circuit monitors the generated negative voltage and provides control signals back to the charge pump circuit. This feedback loop enables precise control of the negative voltage generation process, improving accuracy while the latch circuit maintains the output state to reduce continuous power consumption.
Solution Approach 2:
The invention introduces dynamic control of the charge pump circuit through the comparator and latch circuitry. The charge pump operation is dynamically adjusted based on the comparison results, allowing the circuit to switch between active voltage generation and standby states, thereby optimizing power consumption while maintaining voltage generation accuracy.
3Manufacturing precision
If the threshold voltage of an OS transistor is controlled by introducing impurities like in Si transistors, then the threshold voltage can be adjusted, but reliable technology for controlling OS transistor threshold voltage has not yet been established
Solution Approach 1:
The invention replaces the mechanical/chemical impurity introduction method with an electrical field control mechanism. By applying voltages to the backgate of the OS transistor, the threshold voltage is controlled through electric field effects rather than physical impurity modification, providing reliable and reversible threshold voltage adjustment specific to oxide semiconductor technology.
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 high-accuracy generation of negative voltages with reduced power consumption, stabilizing the operation of semiconductor devices and improving the control of threshold voltages in oxide semiconductor transistors.
Implementation Method 1
A negative potential can be generated by a charge pump circuit
Implementation Method 2
The differential input circuit includes a differential pair of a first n-channel transistor and a second n-channel transistor
Data Source
AI summary
Provided is a comparison circuit to which a negative voltage to be compared can be input directly. The comparison circuit includes a first input terminal, a second input terminal, a first output terminal, and a differential pair. The comparison circuit compares a negative voltage and a negative reference voltage and outputs a first output voltage from the first output terminal in response to the comparison result. The negative voltage is input to the first input terminal. A positive reference voltage is input to the second input terminal. The positive reference voltage is determined so that comparison is performed. The differential pair includes a first n-channel transistor and a second n-channel transistor each having a gate and a backgate. The first input terminal is electrically connected to the backgate of the first n-channel transistor. The second input terminal is electrically connected to the gate of the second n-channel transistor.