Digital Temperature Compensation in Logarithmic TIAs
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing temperature compensation methods for logarithmic transimpedance amplifiers introduce errors due to the use of analog circuitry, impeding accurate determination of input current.
Innovation Solution
Perform temperature compensation in the digital domain by calculating the logarithm of the input current using analog signals sampled by an analog-to-digital converter and a processor, determining a temperature compensation factor based on internal temperature signals to remove temperature dependence from the logarithmic output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If temperature compensation is implemented using analog circuitry, then temperature dependence is compensated, but measurement precision deteriorates due to introduced errors
Solution Approach 1:
The patent replaces the analog circuitry system with a digital processing system. Specifically, analog-to-digital converters transform the analog output signals into digital domain, where mathematical operations including temperature compensation calculations are performed using digital signal processing. This substitution eliminates the inherent errors of analog circuitry while maintaining temperature compensation capability through algorithmic computation.
Solution Approach 2:
The patent introduces digital signal processing as an intermediary between the analog logarithmic transimpedance amplifier and the final measurement output. The intermediary performs multiple functions: converting analog signals to digital format, applying temperature compensation algorithms, and calculating the final input current value. This intermediary layer isolates the measurement from temperature-dependent analog errors while preserving the essential measurement function.
2Stability of the object's composition
If analog circuitry is used for temperature compensation, then temperature stability is improved, but device complexity increases due to additional analog components
Solution Approach 1:
The patent makes the digital signal processor multi-functional by combining several operations into a single digital processing unit. The same processor that converts analog-to-digital also performs temperature compensation calculations and input current determination. This consolidates multiple functions into one component, reducing overall device complexity compared to having separate analog circuits for each function.
Solution Approach 2:
The patent changes the domain parameter from analog to digital. By performing temperature compensation in the digital domain rather than analog domain, the system leverages the flexibility of digital parameter manipulation. Temperature compensation is achieved through software algorithms that can be easily adjusted and optimized without changing physical circuit components, thereby simplifying the hardware architecture.
3Measurement precision
If digital domain processing is used, then measurement precision is improved, but device complexity increases due to analog-to-digital conversion requirements
Solution Approach 1:
The patent performs preliminary analog-to-digital conversion of the output signals before they undergo temperature compensation and final calculation. By converting the signals to digital format early in the processing chain, subsequent operations can be performed with high precision using digital arithmetic. This preliminary action enables accurate measurement while the complexity is managed through efficient use of standard ADC components.
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 superior performance and flexibility by providing a more accurate calculation of the input current, enabling adjustments and corrections not feasible with analog circuitry.
Implementation Method 1
an optical log converter (or optolog converter) is a device used to measure optical power using a photodiode that generates an output current that increases with the optical power
Implementation Method 2
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
Data Source
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.