Amplifier Offset Drift Compensation via Segmented Current Trim
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Solution Overview
Problem
Existing methods for compensating temperature drift in amplifiers and voltage references, such as dynamic offset cancellation techniques, are inefficient for high-speed circuits and cannot effectively minimize offset and temperature drift.
Innovation Solution
A temperature drift compensation apparatus and method using variable current sources, converters, and a controller to generate currents proportional and invariant to temperature, with trim codes to adjust and compensate for inherent offsets, allowing for effective trimming of offset voltages at different temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dynamic offset cancellation techniques (auto-zero and chopping) are used, then offset and temperature drift are minimized for low speed precision amplifiers, but these techniques cannot be efficiently used for high speed circuits
Solution Approach 1:
The offset compensation is divided into two independent segments: a static compensation component that corrects the dominant offset at a given temperature, and a dynamic temperature drift compensation component that tracks and compensates for temperature-induced drift. This segmentation allows the high-speed signal path to remain undisturbed while offset correction occurs through separate, speed-independent mechanisms.
Solution Approach 2:
The static offset compensation is performed in advance during manufacturing or initialization, storing the compensation value in memory. This preliminary action eliminates the need for continuous real-time correction of the dominant offset, allowing high-speed operation without the overhead of dynamic cancellation techniques.
2Speed
If no offset compensation is applied, then the circuit operates at full speed, but significant temperature drift of offset voltage occurs
Solution Approach 1:
A temperature sensor acts as an intermediary element that monitors the temperature of the amplifier and provides this information to the offset compensation circuitry. This mediator enables the system to respond to temperature changes without disrupting the high-speed signal path, maintaining both speed and stability.
Solution Approach 2:
The system performs self-compensation by automatically adjusting the offset correction based on temperature feedback. The controller retrieves stored compensation values and applies them through DACs without requiring external intervention, maintaining stable operation across temperature ranges while preserving full circuit speed.
3Measurement precision
If complex dynamic cancellation techniques are implemented, then offset drift is reduced, but device complexity and implementation difficulty increase
Solution Approach 1:
The patent uses readily available, simple components such as temperature sensors, DACs, and memory devices to implement offset compensation, replacing the need for complex dynamic cancellation circuitry. These standard components are easier to manufacture and integrate, reducing overall device complexity while achieving effective compensation.
Solution Approach 2:
The system changes the parameter being compensated from a dynamic, continuous correction approach to a discrete, temperature-based lookup approach. By storing compensation values in memory and retrieving them based on temperature readings, the system simplifies the compensation mechanism while maintaining effectiveness across different operating conditions.
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 effectively compensates for temperature drift in amplifiers and voltage references, improving drift performance and reducing residual offset voltages across temperature ranges without introducing additional offset, even when using high-speed circuits.
Implementation Method 1
a first variable current source configured to generate a first current proportional to temperature
Implementation Method 2
a second variable current source configured to generate a second current substantially invariable to temperature drift
Implementation Method 3
a first converter configured to receive a first trim code and generate, based on the first trim code, a first converted current from the first current
Data Source
AI summary
Practical electronics such as amplifiers or voltage references can have circuit imbalances due to manufacturing imperfections. For example, amplifiers can have an undesirable offset voltage. The offset voltage might also drift with temperature making the design of these devices difficult. Disclosed are techniques which decrease the amount of offset voltage which provide predictability of device parameters over a range of temperatures.