Optical Receiving Circuit Pulse Width Distortion Reduction
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Solution Overview
Problem
Existing optical receiving circuits face challenges in reducing pulse width distortion, particularly in high-speed signal transmission and diverse data patterns, where pulse width distortion is exacerbated by unstable differential amplifiers and varying data patterns.
Innovation Solution
The optical receiving circuit incorporates a first transimpedance amplifier, a second transimpedance amplifier connected to a light-shielded photodiode, a differential amplifier, a voltage source with an offset voltage, and a transconductance amplifier with a conversion element to accurately match the voltage signal with a threshold, reducing pulse width distortion through appropriate selection of transconductance, resistance, and offset voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a level shift circuit is used to shift the voltage signal, then pulse width distortion is reduced, but the circuit complexity increases and effectiveness is limited to specific conditions
Solution Approach 1:
The patent changes the operating parameters of the transimpedance amplifier by introducing a variable resistance element (such as a MOS transistor operating in different regions) that can dynamically adjust the transimpedance gain. This allows the circuit to adapt to different signal conditions and maintain pulse width accuracy without requiring complex external level shift circuits.
Solution Approach 2:
The transimpedance amplifier is designed to perform multiple functions: it converts photodiode current to voltage, provides gain adjustment, and inherently handles pulse width preservation. By integrating these functions into a single circuit block, the patent reduces overall circuit complexity while maintaining the ability to reduce pulse width distortion across diverse data patterns.
2Device complexity
If existing light receiving circuits are used, then circuit simplicity is maintained, but pulse width distortion occurs during high-speed data transmission and diverse data patterns
Solution Approach 1:
The patent introduces dynamic adjustment capability to the transimpedance amplifier by using a variable resistance element that can change its resistance value based on operating conditions. This dynamic adjustment allows the circuit to optimize its transimpedance gain for high-speed data transmission and diverse data patterns, thereby maintaining pulse width accuracy without requiring a completely complex circuit architecture.
Solution Approach 2:
The circuit employs feedback mechanisms where the output signal or a portion of it is fed back to adjust the transimpedance amplifier's operating point. This self-adjusting capability allows the circuit to automatically compensate for pulse width distortion under varying data patterns and transmission speeds, maintaining accuracy while keeping the overall circuit structure relatively simple.
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 effectively reduces pulse width distortion and maintains stability across diverse data patterns, ensuring high-quality signal transmission in optical couplers and data links, especially in industrial equipment.
Implementation Method 1
an optical digital signal is converted to an electrical digital signal by a light receiving circuit. The light receiving circuit includes photodiodes
Implementation Method 2
a first transimpedance amplifier configured to convert an input signal to a voltage signal, the input signal being current-converted by a first photodiode
Implementation Method 3
a differential amplifier having a first terminal and a second terminal, and being configured to amplify a difference between the voltage signal inputted to the first terminal and a signal inputted to the second terminal
Implementation Method 4
a transconductance amplifier configured to receive as input a branch of the voltage signal and output a current signal to the second terminal
Implementation Method 5
a conversion element provided between the voltage source and the second terminal, and being configured to voltage-convert the current signal
Data Source
AI summary
A light receiving circuit includes: a first transimpedance amplifier configured to convert an input signal to a voltage signal, the input signal being current-converted by a first photodiode; a second transimpedance amplifier connected to a light-shielded second photodiode, and being configured to output a reference voltage; a differential amplifier; a transconductance amplifier; a voltage source; and a conversion element. The differential amplifier has a first terminal and a second terminal, and amplifies a difference between the voltage signal inputted to the first terminal and a signal inputted to the second terminal. The transconductance amplifier receives as input a branch of the voltage signal and outputs a current signal to the second terminal. The voltage source superimposes an offset voltage on the output voltage of the second transimpedance amplifier. The conversion element is provided between the voltage source and the second terminal, and voltage-converts the current signal.