APD Bias Circuit Using Breakdown Diodes for Stable Gain
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Solution Overview
Problem
The gain of an avalanche photodiode (APD) changes with ambient temperature fluctuations, making it difficult to maintain a desired gain consistently.
Innovation Solution
A light detection device incorporating a plurality of temperature compensation diodes with different breakdown voltages, connected in parallel with the APD, allows for selecting a desired gain by applying a bias voltage corresponding to the breakdown voltage of the selected diode, thereby stabilizing the gain against temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a constant bias voltage is applied to the APD, then the device structure is simple, but the gain of the APD changes as the ambient temperature changes
Solution Approach 1:
The patent applies parameter changes by using multiple temperature compensation diodes with different breakdown voltages to dynamically adjust the bias voltage applied to the APD. This allows the gain to be stabilized at different temperature conditions by selecting the appropriate diode, thus resolving the contradiction between simple device structure and gain stability.
Solution Approach 2:
The patent implements dynamics by making the bias voltage adjustable through a switching circuit that can select between multiple temperature compensation diodes. This dynamic adjustment capability allows the system to adapt to temperature changes while maintaining gain stability, overcoming the limitation of constant bias voltage.
2Reliability
If the breakdown voltage difference between APD and bias voltage is controlled to be constant, then the gain stability improves, but the adaptability to switch gain deteriorates
Solution Approach 1:
The patent segments the temperature compensation function into multiple discrete diodes, each with a specific breakdown voltage. This segmentation allows the system to provide stable gain through each individual diode while also enabling adaptability by switching between different diodes, thus resolving the contradiction between gain stability and gain switching capability.
Solution Approach 2:
The patent achieves multi-functionality by designing a circuit that can both stabilize gain (through constant difference voltage control) and switch gain (through selective diode activation). The switching circuit enables the same system to perform both functions, resolving the contradiction between reliability and adaptability.
3Adaptability or versatility
If multiple temperature compensation diodes with different breakdown voltages are used, then the gain adaptability improves, but the device complexity increases
Solution Approach 1:
The patent introduces a switching circuit as an intermediary component that manages the complexity of multiple temperature compensation diodes. This mediator selectively connects the appropriate diode to the APD, enabling gain adaptability while keeping the overall circuit structure manageable through controlled switching rather than permanent complex connections.
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 device achieves stable gain in the APD by dynamically adjusting the bias voltage based on the breakdown voltage of the temperature compensation diodes, ensuring consistent performance across varying temperatures.
Implementation Method 1
a voltage corresponding to the breakdown voltage of a temperature compensation diode is applied to the avalanche photodiode as a bias voltage
Data Source
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AI summary
A light detection device 1 includes an APD 11, a plurality of temperature compensation diodes 26, 27, and 28, and a circuit unit 3. The plurality of temperature compensation diodes 26, 27, and 28 have different breakdown voltages lower than a breakdown voltage of the APD 11. The circuit unit 3 puts any one of the plurality of temperature compensation diodes 26, 27, and 28 into a breakdown state. The circuit unit 3 includes a plurality of terminals 25 and a terminal 22. The plurality of terminals 25 are respectively connected to electrodes 29b of the mutually different temperature compensation diodes 26, 27, and 28. The terminal 22 is electrically connected to the APD 11 and electrodes 29a of the temperature compensation diodes 26, 27, and 28.