Photodiode Detection Circuit With Dynamic Resistance Noise Damping
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Solution Overview
Problem
Detection circuits with photodiodes face noise issues due to resonant circuits formed by inductance and capacitance, which introduce peaks and distortions, and existing damping methods increase thermal noise, making it challenging to maintain a low noise level while maintaining a desired quality factor.
Innovation Solution
Incorporating a dynamic resistance circuit with a DC bias current to set its resistance, reducing thermal noise by half compared to traditional resistors, and using this circuit in conjunction with a transimpedance amplifier to amplify photodiode current while maintaining a specific quality factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a damping resistor is provided to prevent resonant circuit peaks and distortions, then the quality factor is improved, but thermal noise increases
Solution Approach 1:
The patent changes the resistance value dynamically rather than using a fixed damping resistor. By varying the resistance parameter according to operating conditions, the circuit achieves optimal quality factor while minimizing thermal noise generation at different signal levels and frequencies.
Solution Approach 2:
The patent employs a dynamic resistance element that adjusts its resistance value in real-time based on circuit conditions. This dynamic adjustment allows the resistance to provide optimal damping for quality factor control while reducing thermal noise generation compared to a static resistor operating at fixed high resistance values.
2Power
If the photodiode current is amplified using a transimpedance amplifier, then the signal strength is improved, but the noise from the damping resistor becomes more significant
Solution Approach 1:
The patent dynamically adjusts the damping resistance parameter to optimize the signal-to-noise ratio. By changing the resistance value based on operating conditions, the circuit maintains effective noise suppression while allowing the transimpedance amplifier to achieve maximum signal amplification without being limited by excessive thermal noise.
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 reduces thermal noise by half while maintaining the desired quality factor, thereby enhancing the detection circuit's performance and reducing distortions.
Implementation Method 1
a photodiode that is configured to convert radiation to a photodiode current
Implementation Method 2
Incorporating a dynamic resistance circuit with a DC bias current to set its resistance, reducing thermal noise by half compared to traditional resistors
Data Source
AI summary
A method and a detection circuit. The detection circuit may include (a) a photodiode that is configured to convert radiation to a photodiode current; (b) a photodiode bias circuit that is configured to bias the photodiode; (c) a dynamic resistance circuit that has a first terminal and a second terminal; (d) a transimpedance amplifier that is configured to amplify an output current of the dynamic resistance circuit to provide an output voltage, wherein the second terminal is coupled to a negative input port of the amplification circuit; and (e) a conductor that is coupled between the first terminal and an anode of the photodiode.