Offset Drift Trimming Circuit Using Temperature-Dependent Current Sources

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Amplifiers face challenges in reducing offset drift, which is temperature-dependent and requires multiple trimming steps in bipolar and MOSFET technologies, making existing solutions complex and area-intensive.

Innovation Solution

A drift trimming stage with four current sources having different temperature dependencies is used to generate trimming currents, which are combined across resistors to create a voltage drop that compensates for offset drift, eliminating the need for digital components and simplifying the circuitry.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional trimming methods are used for JFET or MOSFET amplifiers, then offset and offset drift can be reduced, but the device complexity increases due to requiring multiple trimming steps and digital components

Engineering Contradiction:

Improveoffset drift compensationVSAvoidtrimming circuit complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces digital trimming components (switches, resistors, capacitors controlled by digital signals) with an analog trimming circuit using current sources and operational amplifiers. The analog circuit continuously adjusts trimming currents based on temperature-dependent characteristics, eliminating the need for digital control logic and associated components, thus reducing device complexity while maintaining offset drift compensation capability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent utilizes temperature-dependent parameters of current sources to automatically adjust trimming currents. By designing current sources with specific temperature coefficients, the circuit dynamically changes trimming parameters in response to temperature variations, achieving continuous offset drift compensation without complex digital control mechanisms

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If digital components are used for offset trimming, then precise control is achieved, but the chip area increases significantly

Engineering Contradiction:

Improveoffset trimming precisionVSAvoidchip area

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The operational amplifier-based trimming circuit serves multiple functions: it provides continuous analog control of trimming currents, automatically compensates for temperature drift through inherent temperature-dependent characteristics of current sources, and eliminates the need for separate digital control logic. This multi-functionality reduces the overall chip area required for the trimming subsystem

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If multiple trimming steps are applied at different temperatures, then offset and offset drift are reduced in JFET or MOSFET amplifiers, but the manufacturing process becomes more complex

Engineering Contradiction:

Improveoffset drift compensationVSAvoidtrimming process simplicity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent incorporates temperature-dependent current sources designed during the manufacturing process to automatically provide appropriate trimming currents at different operating temperatures. The current sources are pre-configured with specific temperature coefficients, enabling the circuit to perform trimming actions appropriate for each temperature condition without requiring external intervention or complex manufacturing processes

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The trimming circuit uses the inherent temperature-dependent characteristics of its current sources to automatically adjust trimming parameters in response to temperature variations. The circuit self-regulates without requiring external control signals or complex manufacturing processes, as the temperature dependence is built into the circuit design itself, simplifying the manufacturing process

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS8212606B2Apparatus and method for offset drift trimming

Publication Date: 2012.07.03 TEXAS INSTRUMENTS INC

AI summary

An apparatus is provided that includes a drift trimming stage that includes a first current source providing a current with a first temperature dependency and a second current source providing a current with a second temperature dependency. The first and the second current source are coupled at a first node and configured to have equal currents at a first temperature. There is further a third current source providing a current with a third temperature dependency and a fourth current source providing a current with a fourth temperature dependency. The third current source and the fourth current source are coupled at a second node and configured to have equal currents at the first temperature. There is a first resistor coupled between the first node and a third node, a second resistor coupled between the second node and the third node. The first node and the second node are coupled to provide a combined voltage drop across the first resistor and the second resistor for reducing the offset drift.