Two-Stage Sense Amplifier With Output Stabilization for Low-Power Memory

Solution Overview

Problem

Conventional sense amplifier circuits in semiconductor memory devices face challenges in achieving high amplification gain and stability, especially at low voltages, due to increased load and instability issues related to the distance between the I/O sense amplifier and the memory cell array, and require large transistors which increase current consumption and circuit size.

Innovation Solution

A sense amplifier circuit that combines a current sense amplifier and a voltage sense amplifier, with an output stabilizing circuit having a positive input resistance, allowing the current sense amplifier to amplify differential input currents and generate differential output voltages, which are then amplified by the voltage sense amplifier, and the output stabilizing circuit ensures stability, reducing current dissipation and power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If current sense amplifiers are used to increase amplification gain, then the amplification capability is improved, but the input resistance becomes negative causing instability

Engineering Contradiction:

Improveamplification gainVSAvoidcircuit stability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The sense amplifier is divided into two separate stages: a current sense amplifier for high-gain amplification and a voltage sense amplifier for stable voltage sensing. This segmentation allows each stage to perform its specialized function without the instability issues affecting the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A buffer circuit is introduced as an intermediary between the current sense amplifier and the voltage sense amplifier. This buffer isolates the negative input resistance of the current amplifier from the voltage amplifier, preventing instability while maintaining high amplification gain.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If transistor sizes in current sense amplifier are increased to improve stability, then the stability is improved, but the circuit size and current consumption are significantly increased

Engineering Contradiction:

Improvecircuit stabilityVSAvoidcurrent consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The sense amplifier is divided into two separate stages: a current sense amplifier for high-gain amplification and a voltage sense amplifier for stable voltage sensing. This segmentation allows each stage to perform its specialized function without the instability issues affecting the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the operating parameters by using a buffer circuit with high input impedance to connect the current sense amplifier to the voltage sense amplifier. This allows the voltage sense amplifier to operate with smaller transistor sizes while maintaining stability, reducing current consumption.

Inventive Principle:

Principle #35Parameter changes

3Length of moving object

If the distance between I/O sense amplifier and memory cell array is increased, then the signal transmission capability is improved, but the sensing capability deteriorates due to voltage difference attenuation

Engineering Contradiction:

Improvesignal transmission distanceVSAvoidvoltage sensing capability

Core Design Contradiction:

Length of moving objectVSMeasurement precision

Solution Approach 1:

The current sense amplifier rapidly amplifies the small voltage differences from the memory cell array before they can attenuate during transmission. This rapid amplification 'skips' over the attenuation problem by establishing strong differential signals early in the transmission path.

Inventive Principle:

Principle #21Skipping (Rushing through)

Solution Approach 2:

A buffer circuit is introduced as an intermediary between the current sense amplifier and the voltage sense amplifier. This buffer isolates the negative input resistance of the current amplifier from the voltage amplifier, preventing instability while maintaining high amplification gain.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS7800970B2Sense amplifier and semiconductor memory device having the same

Publication Date: 2010.09.21 SAMSUNG ELECTRONICS CO LTD

AI summary

A sense amplifier circuit includes a current sense amplifier, a voltage sense amplifier, and an output stabilizing circuit. The current sense amplifier amplifies differential input currents to generate differential output voltages and provides the differential output voltages to a sense amplifier output line pair. The voltage sense amplifier is coupled to the sense amplifier output line pair to amplify the differential output voltages on the sense amplifier output line pair. The voltage sense amplifier is activated at the time later than a time of activation of the current sense amplifier. The output stabilizing circuit is coupled to the sense amplifier output line pair to stabilize the differential output voltages on the sense amplifier output line pair. The output stabilizing circuit has a positive input resistance. Accordingly, the sense amplifier circuit reduces power consumption and an occupied area on a semiconductor chip.