Laser Driver Circuit With Feedback Noise Rejection for Mobility Measurement
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Solution Overview
Problem
Current laser driver circuits for measuring electrophoretic mobility suffer from noise instability and sensitivity to power supply rail noise, particularly in the frequency range of 8 kHz to 100 kHz, leading to inaccurate particle size measurements.
Innovation Solution
A laser driver circuit comprising a voltage regulator, operational amplifier, transistor, resistors, and capacitors that actively suppress power supply noise and allows for controlled current flow to the laser, incorporating a low noise precision operational amplifier and n-channel MOSFET for improved noise performance and current limiting capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional laser driver circuits are used, then the circuit is simple, but noise instability and sensitivity to power supply rail noise occur in the frequency range of 8 kHz to 100 kHz
Solution Approach 1:
A feedback circuit is introduced as an intermediary between the power supply and the laser driver. This feedback circuit monitors the output signal and adjusts the drive signal to compensate for power supply noise, thereby improving noise stability without directly modifying the power supply itself.
Solution Approach 2:
The patent implements a feedback mechanism that detects output signal variations caused by power supply noise and dynamically adjusts the laser drive current accordingly. This closed-loop control suppresses the impact of power supply fluctuations in the 8 kHz to 100 kHz frequency range.
2Measurement precision
If conventional laser driver circuits are used, then the device is simple, but inaccurate particle size measurements result due to noise instability
Solution Approach 1:
The feedback circuit continuously monitors the output signal and adjusts the drive signal to maintain measurement accuracy despite power supply noise. This ensures precise particle size measurements by compensating for noise-induced signal variations in real-time.
Solution Approach 2:
The feedback circuit acts as an intermediary that isolates the measurement process from power supply noise. By processing and conditioning the drive signal before it reaches the laser, it protects the measurement accuracy from external noise interference.
3Power
If higher current is applied to the laser, then the optical power output increases, but noise instability worsens in the frequency range of 8 kHz to 100 kHz
Solution Approach 1:
The feedback mechanism detects noise-induced variations in the laser output and dynamically adjusts the drive current to compensate. This allows the system to operate at higher power levels while maintaining noise stability through active compensation.
Solution Approach 2:
The feedback circuit serves as an intermediary that decouples the relationship between drive current and output power. It allows higher current operation by filtering out noise effects, enabling high power output with maintained stability.
Data Source
AI summary
The present disclosure describes a laser driver circuit for measuring electrophoretic mobility of a sample. In an exemplary embodiment, the circuit includes a voltage regulator circuit to receive an input voltage and to output a stable output voltage, an operational amplifier electrically coupled to an output of the voltage regulator circuit, a transistor electrically coupled to an output of the operational amplifier and to the output of the voltage regulator circuit, a plurality of resistors electrically coupled to the operational amplifier and to the transistor, a plurality of capacitors electrically coupled to the operational amplifier, to the transistor, and to the plurality of resistors, and where the operational amplifier is to output a voltage to adjust a gate voltage of the transistor such that a drain source resistance of the transistor allows a controlled current to flow to a laser for measuring electrophoretic mobility of a sample.