Digital Temperature Compensation for Logarithmic Transimpedance Amplifiers

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Solution Overview

Problem

Existing temperature compensation methods for logarithmic transimpedance amplifiers introduce errors in determining input current due to reliance on analog circuitry, which is inaccurate.

Innovation Solution

Perform temperature compensation in the digital domain using a logarithmic transimpedance amplifier device that calculates the logarithm of input current based on internal analog signals, employing an analog-to-digital converter and a processor to determine a temperature compensation factor, thereby removing temperature dependence from the output voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If temperature compensation is performed using analog circuitry, then temperature dependence is addressed, but measurement precision deteriorates due to introduced errors

Engineering Contradiction:

Improvetemperature compensationVSAvoidinput current determination accuracy

Core Design Contradiction:

TemperatureVSMeasurement precision

Solution Approach 1:

The patent replaces the analog circuitry system with a digital processing system. Specifically, it substitutes analog temperature compensation circuits with digital signal processing that reads thermometer signals, calculates compensation factors, and applies corrections digitally to determine input current accurately without analog circuit errors

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces digital signal processing as an intermediary between the analog thermometer signal and the final input current measurement. The intermediary digitally processes the temperature signal, calculates compensation factors, and applies corrections before determining the final measurement, thereby isolating the precise measurement from analog circuit errors

Inventive Principle:

Principle #24Intermediary (Mediator)

2Temperature

If analog circuitry is used for temperature compensation, then temperature effects are mitigated, but device complexity increases due to additional analog components

Engineering Contradiction:

Improvetemperature independenceVSAvoidcircuitry complexity

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The patent substitutes complex analog temperature compensation circuitry with a simplified digital processing approach. Instead of adding analog components, it uses digital signal processing to read existing thermometer signals and apply compensation algorithms, thereby achieving temperature independence without increasing analog device complexity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent extracts the temperature compensation function from the analog circuit domain and relocates it to the digital processing domain. By separating the temperature sensing (analog) from the temperature compensation calculation (digital), it eliminates the need for complex analog compensation circuitry while maintaining temperature independence

Inventive Principle:

Principle #2Taking out (Extraction)

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

Achieves accurate and flexible temperature-independent determination of input current by correcting for residual leakage and emitter-resistance using digital domain calculations.

Implementation Method 1

an optolog converter includes a logarithmic transimpedance amplifier (TIA) device that relies on the logarithmic relationship between base-emitter voltage and collector current of bipolar junction transistors

Methodology Applied

Scientific EffectLogarithmic relationship between base-emitter voltage and collector current:

Implementation Method 2

generate an analog thermometer signal that is proportional to a temperature of the logarithmic transimpedance amplifier device

Methodology Applied

Scientific EffectTemperature proportionality in analog signal generation:

Data Source

PatentUS20250247055A1Techniques for digital-domain temperature compensation in logarithmic transimpedance amplifier devices

Publication Date: 2025.07.31 ANALOG DEVICES INC

AI summary

Technologies are provided to calculate a logarithm of an input current to a logarithmic transimpedance amplifier device at a particular temperature. The logarithm of the current is calculated in digital domain based on sampling of analog signals that are internal to the logarithmic transimpedance amplifier device. The sampling can be performed, in some cases, by an analog-to-digital converter device integrated into the logarithmic transimpedance amplifier device. The calculation in digital domain is performed by one or more processor external to the logarithmic transimpedance amplifier device. The calculation includes a determination of a temperature compensation factor based on an internal analog signal indicative of temperature of the logarithmic transimpedance amplifier device. The temperature compensation factor permits removing temperature dependence from a logarithmic output voltage originating from the input current. Operating in the digital domain permits applying corrections that account for residual leakage current and an emitter-resistance correction at high input currents.