Single-Ended Sense Amplifier Circuit for Low-Voltage Operation
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Solution Overview
Problem
Conventional charge transfer type sense amplifier circuits face difficulties in achieving sufficient operating margin and speed during low-voltage operation, especially when using memory cells with small capacitance, as the capacitance at the sense node increases, hindering amplification operations.
Innovation Solution
A single-ended sense amplifier circuit is employed, utilizing a first MOS transistor to drive the bit line to a predetermined voltage and switch connections based on a gate voltage, and a second MOS transistor to amplify signals, with precharge circuits setting the bit line and sense node to specific potentials to maintain a required voltage difference, allowing operation in both charge transfer and charge distributing modes, even with low-capacitance memory cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a charge transfer type sense amplifier circuit is used to amplify minute signals from memory cells, then the amplification capability is improved, but the capacitance at the sense node increases, which hinders amplification operations during low-voltage operation
Solution Approach 1:
The patent segments the sense amplifier circuit into distinct functional blocks: a sense amplifier unit with transistors Q1-Q4 for signal amplification, a precharge unit with transistors Q5-Q8 for capacitance management, and a control unit. This segmentation allows independent optimization of each unit, enabling the sense amplifier to achieve sufficient gain while managing sense node capacitance through coordinated control of the precharge unit.
Solution Approach 2:
The precharge unit performs preliminary action by precharging the bit line and sense node to predetermined potentials before the amplification phase. This preliminary charging establishes appropriate voltage levels and manages capacitance distribution, ensuring that the sense amplifier can operate reliably during low-voltage conditions without being hindered by excessive sense node capacitance.
2Reliability
If the capacitance at the sense node is reduced to enable low-voltage operation, then the operating margin is improved, but the amplification of minute signals becomes more difficult
Solution Approach 1:
The patent employs dynamic control of the sense amplifier circuit through timed switching of transistors Q1-Q8 based on control signals (e.g., PRECHARGE signal, READ signal). The circuit transitions between different operational states (precharge phase, amplification phase, hold phase), allowing the sense node capacitance to be effectively managed during each phase. This dynamic operation enables sufficient signal amplification while maintaining appropriate voltage margins for low-voltage operation.
Solution Approach 2:
The patent changes operational parameters dynamically: the precharge unit adjusts bit line voltage to predetermined levels, the sense amplifier unit modifies gain characteristics through transistor switching, and the control unit adjusts timing parameters. These parameter changes enable the circuit to achieve both sufficient amplification of minute signals and maintain adequate operating margins during low-voltage operation.
3Measurement precision
If a latch type differential amplifier is used for signal amplification, then the amplification gain is improved, but the circuit scale increases
Solution Approach 1:
The sense amplifier unit with transistors Q1-Q4 serves multiple functions: it amplifies the differential signal from the bit line, latches the amplified signal, and can be controlled to operate in different modes (amplification, hold, reset). This multi-functionality eliminates the need for separate latch circuits, reducing overall circuit scale while maintaining sufficient amplification gain and signal integrity.
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
This configuration ensures sufficient operating margin and speed in low-voltage operations, particularly effective for memory cells with small capacitance, and allows for a smaller circuit scale and improved reliability, enhancing production yield and reducing manufacturing costs.
Implementation Method 1
a first MOS transistor driving the bit line to a predetermined voltage and switching connection between the bit line and a sense node in response to a gate voltage
Implementation Method 2
a second MOS transistor having a gate connected to the sense node and amplifying the signal transmitted from the bit line via the first MOS transistor
Implementation Method 3
a first precharge circuit precharging the bit line to a first potential in response to a first control signal; and a second precharge circuit precharging the sense node to a second potential higher than the first potential
Data Source
AI summary
A single-ended sense amplifier circuit of the invention comprises first and second MOS transistors and first and second precharge circuits. The first MOS transistor drives the bit line to a predetermined voltage and switches connection between the bit line and a sense node and the second MOS transistor whose gate is connected to the sense node amplifies the signal via the first MOS transistor. The first precharge circuit precharges the bit line to a first potential and the second precharge circuit precharges the sense node to a second potential. Before sensing operation, the bit line is driven to the predetermined voltage when the above gate voltage is controlled to decrease. The predetermined voltage is appropriately set so that a required voltage difference at the sense node between high and low levels can be obtained near a changing point between charge transfer/distributing modes.