Photodiode Detection Circuit With Feedback Anti-Blooming Control
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Solution Overview
Problem
Conventional detection circuits suffer from blooming phenomena when exposed to intense light, leading to inaccurate photon collection and biased voltage changes, making them unsuitable for industrial use due to narrow anti-blooming voltage ranges and fabrication constraints.
Innovation Solution
A detection circuit with an anti-blooming circuit that compares the output voltage of a transimpedance amplifier with a setpoint voltage and generates a feedback current to prevent voltage changes, using a field effect transistor connected in parallel to the capacitor or resistor, allowing the anti-blooming voltage to be defined independently of the input voltage, thus preventing blooming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reverse biased photodiode is used to detect light radiation, then photon detection capability is improved, but blooming effect occurs on adjacent photodiodes when exposed to intense light
Solution Approach 1:
The patent implements a feedback mechanism where the output voltage of the transimpedance amplifier is fed back to the gate of the field effect transistor. When intense light causes the output voltage to reach a threshold, the feedback signal activates the transistor to drain excess charge from the capacitor, preventing blooming in adjacent photodiodes while maintaining accurate photon detection capability
Solution Approach 2:
The patent dynamically changes the electrical parameters of the anti-blooming circuit by using a field effect transistor whose gate voltage is controlled by the output signal itself. This parameter change allows the circuit to adapt to varying light intensities, enabling effective blooming prevention across different operating conditions while preserving detection precision
2Object-affected harmful factors
If an nMOS transistor is connected in parallel to the capacitor to prevent bias modification, then blooming is reduced, but the circuit becomes complex and difficult to fabricate industrially
Solution Approach 1:
The patent makes the field effect transistor serve multiple functions: it acts as both the anti-blooming device and the control element for the transimpedance amplifier. This multi-functionality reduces the total component count and simplifies the circuit architecture, making it more suitable for industrial fabrication while maintaining effective blooming prevention
Solution Approach 2:
The anti-blooming circuit is designed to be self-regulating through automatic feedback control. The output voltage automatically controls the transistor activation without requiring external control circuits or additional components, simplifying the overall design and improving ease of manufacture while effectively preventing blooming
3Object-affected harmful factors
If anti-blooming voltage is applied to the gate electrode to keep the photodiode reverse biased, then blooming is prevented, but the voltage range is narrow and requires precise adjustment
Solution Approach 1:
The feedback connection from the output voltage to the gate electrode automatically adjusts the transistor's operating point based on the actual output signal level. This eliminates the need for precise pre-adjustment of anti-blooming voltage, as the system self-regulates according to real-time operating conditions, reducing device complexity while maintaining effective blooming prevention
Solution Approach 2:
The gate voltage is made dynamic rather than static, changing automatically with the output signal level. This dynamic adjustment allows the circuit to adapt to varying light intensities and operating conditions without requiring fixed precise voltage settings, simplifying the device while maintaining effective blooming control across different scenarios
4Measurement precision
If the output voltage increases to represent intense lighting, then light detection accuracy is improved, but the voltage change modifies the photodiode bias and causes blooming
Solution Approach 1:
The feedback mechanism monitors the output voltage that represents light intensity and uses it to control the transistor. When the output voltage increases due to intense lighting, the feedback signal activates the transistor to drain excess charge, preventing bias modification and blooming while preserving the accurate light detection information in the output voltage signal
Solution Approach 2:
The transistor acts as a counterbalancing element that opposes the harmful effect of voltage increase. When the output voltage rises to represent intense lighting, the activated transistor provides an opposing action by draining excess charge from the capacitor, counterweighting the bias modification effect while allowing the output voltage to maintain accurate light intensity representation
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 solution effectively prevents blooming by maintaining a stable output voltage, ensuring accurate photon collection and reliable fabrication, making the circuit more robust and suitable for industrial integration while maintaining a compact and efficient design.
Implementation Method 1
a reverse biased photodiode delivers a current representative of an observed scene
Implementation Method 2
the anti-blooming circuit comprises a field effect transistor connected between the input and the output of the transimpedance amplifier
Data Source
AI summary
The detection circuit comprises a photodiode connected to an input of a capacitive transimpedance amplifier. The circuit comprises an anti-blooming circuit connected between the input and an output of the capacitive transimpedance amplifier. The anti-blooming circuit comprises a field effect transistor connected between the input and output of the capacitive transimpedance amplifier. The transistor is of pMOS type when the input of the capacitive transimpedance amplifier is connected to a cathode of the photodiode. The transistor is of nMOS type when the input of the capacitive transimpedance amplifier is connected to an anode of the photodiode.