Chopper Instrumentation Amplifier for High-Gain Offset Cancellation
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Solution Overview
Problem
Conventional instrumentation amplifiers face limitations in achieving high gain while accurately canceling offset voltages and maintaining stability over a wide range of common mode input voltages, leading to distorted output signals and limited sensitivity in detecting small resistance changes in semiconductor memory devices.
Innovation Solution
A chopper instrumentation amplifier is introduced, comprising multiple amplifier stages with chopper circuits to cancel offset voltages and low-pass filters to remove the square wave imposed by the chopper circuit, allowing for high-gain operation without distorting the signal, and a non-chopper amplifier stage for final signal amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional instrumentation amplifiers are used to achieve high gain, then signal amplification is improved, but offset voltage cancellation accuracy deteriorates and output signal distortion occurs
Solution Approach 1:
The amplifier is divided into multiple stages: a first amplifier stage that provides initial gain, a chopper stage that processes the signal at intermediate levels, and a second amplifier stage that provides final gain. This segmentation allows offset cancellation to occur at the intermediate chopper stage before full amplification, improving both gain and offset cancellation accuracy simultaneously
Solution Approach 2:
A chopper circuit is introduced as an intermediary between the two amplifier stages. This chopper circuit converts the amplified signal from the first stage into a form that can be processed with better offset cancellation, acting as a mediator that enables both high gain and accurate offset cancellation by transforming the signal at an intermediate point in the amplification process
2Adaptability or versatility
If conventional instrumentation amplifiers operate over a wide range of common mode voltages, then adaptability is improved, but stability deteriorates leading to distorted output signals
Solution Approach 1:
The chopper circuit introduces dynamic switching operation that adapts the amplifier's characteristics during operation. By periodically switching the chopper circuit on and off, the system can maintain stability across varying common mode voltages while preserving the ability to operate over a wide voltage range, as the dynamic operation allows the circuit to adjust to different input conditions
3Measurement precision
If conventional instrumentation amplifiers amplify small resistance changes, then sensitivity is improved, but offset voltages cause signal distortion
Solution Approach 1:
The first amplifier stage performs preliminary amplification of the small signal before it reaches the chopper stage. This preliminary action boosts the small resistance change signal to a level where it can be effectively processed by the chopper circuit, which then cancels offset voltages. The combination allows sensitive detection of small resistance changes while maintaining signal integrity through subsequent offset cancellation
Solution Approach 2:
The chopper circuit converts the harmful effect of offset voltages into a beneficial cancellation mechanism. By modulating the signal through the chopper stage, offset voltages are transformed into a form that can be easily filtered and canceled, turning what would be a source of distortion into a means of achieving both high sensitivity and clean output signals
Data Source
AI summary
Embodiments of the disclosure are drawn to apparatuses and methods for a chopper instrumentation amplifier. For a variety of applications, such as testing the resistance of connections between layers of a memory, it may be desirable to provide a high gain instrumentation amplifier. A chopper instrumentation amplifier may provide a high gain while allowing a wide range of common input voltages and a canceling an offset on the amplifier. An example chopper instrumentation amplifier of the present disclosure may include a plurality of amplifiers including chopper amplifiers and non-chopper amplifiers. The chopper amplifiers may use chopper circuits to cancel out an offset voltage of the amplifiers. Low pass filters may be used to minimize the impact of the chopper amplifiers.