Photoconductor Readout Circuit with Capacitive Dark Current Blocking
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Solution Overview
Problem
Photoconductors, such as lead sulfide photoconductors, exhibit strong drift in signal resistance due to environmental changes, leading to complex and costly circuitry with poor signal-to-noise ratio in readout systems, particularly in spectrometers and other applications requiring multiple sensors.
Innovation Solution
A device comprising a photoconductor readout circuit with a voltage divider circuit, a reference resistor, and a capacitor between the amplifier input and voltage divider output, which blocks dark current and amplifies the modulated current using a charge or transimpedance amplifier, reducing the number of components and noise sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If voltage divider circuits with operational amplifiers are used to read out photoconductors, then the signal can be amplified, but the circuit complexity and number of components increases linearly with the number of pixels
Solution Approach 1:
The patent merges the voltage divider and amplifier functions into a single integrated circuit device. The readout circuit includes a voltage divider network with resistors and an operational amplifier configured to simultaneously perform voltage division and signal amplification, reducing the total component count compared to separate discrete circuits for each pixel.
Solution Approach 2:
The integrated readout circuit is designed to handle multiple photoconductor pixels through a single device. The circuit can selectively read out signals from different pixels by switching between them, providing multi-functionality that reduces the need for dedicated circuitry for each pixel while maintaining signal amplification capabilities.
2Ease of operation
If multiple resistors are used in the readout circuit, then voltage division and signal processing can be achieved, but electrical noise from resistors degrades the signal-to-noise ratio
Solution Approach 1:
The patent optimizes the resistance values and configurations in the voltage divider network to minimize thermal noise while maintaining proper voltage division ratios. By carefully selecting resistor parameters and using low-noise resistor types, the circuit achieves good signal processing capability with reduced electrical noise interference.
3Ease of manufacture
If photoconductors are biased with DC voltage to detect electromagnetic absorption, then the detector responds to illumination, but dark current flows through the device which masks the small signal current
Solution Approach 1:
The circuit design extracts and separates the dark current component from the total current through the photoconductor. The readout circuit measures the total current and uses the known dark current characteristics to isolate and measure only the small signal current component caused by electromagnetic illumination, effectively removing the harmful dark current effect from the measurement.
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
This configuration significantly reduces circuit complexity and improves the signal-to-noise ratio, enabling more efficient and cost-effective readout of photoconductors, especially in multi-pixel arrays, by isolating the dark current and amplifying the signal of interest.
Implementation Method 1
at least one capacitor arranged between an input of the amplifier device and an output of the voltage divider circuit
Implementation Method 2
at least one photoconductor configured for exhibiting an electrical resistance dependent on an illumination of a light-sensitive region of the photoconductor
Data Source
AI summary
Disclosed herein is a device includingat least one photoconductor configured for exhibiting an electrical resistance dependent on an illumination of a light-sensitive region of the photoconductor; andat least one photoconductor readout circuit, where the photoconductor readout circuit includes at least one voltage divider circuit, where the voltage divider circuit includes at least one reference resistor Rref being arranged in series with the photoconductor, where the photoconductor readout circuit includes at least one amplifier device, where the photoconductor readout circuit includes at least one capacitor arranged between an input of the amplifier device and an output of the voltage divider circuit.