Optical Receiving Circuit With Adaptive Resistance Distortion Control
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Solution Overview
Problem
Differential amplifiers in optical receiving circuits face distortion issues as differential current increases, particularly in converting differential currents from photodetectors into differential voltages, due to limitations in existing techniques for managing input current and suppressing voltage distortion.
Innovation Solution
A receiving circuit design incorporating a differential amplifier with a control circuit that adjusts the resistance values of variable resistive elements, utilizing inductors and FETs to manage differential current signals, thereby detecting and mitigating distortion by controlling the impedance and current flow based on differential voltage amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the differential current increases to improve signal amplification, then the gain is improved, but distortion of the differential voltage is generated
Solution Approach 1:
The patent applies dynamics by making the resistance values variable rather than fixed. The first and second variable resistive elements (implemented as FETs) dynamically adjust their resistance values based on control signals generated by the control circuit. This allows the input circuit to adapt its impedance characteristics in real-time, enabling high gain operation while suppressing distortion through active control of the differential current flow.
Solution Approach 2:
The patent changes the resistance parameter of the input circuit elements from fixed to variable. By controlling the resistance values of the first and second variable resistive elements based on the differential voltage amplitude, the system can optimize the trade-off between gain and distortion. The control circuit adjusts these parameters dynamically to maintain optimal performance across different operating conditions.
2Speed
If the resistance values are reduced to increase current flow and gain, then the gain band is expanded, but group delay degradation increases
Solution Approach 1:
The patent dynamically changes the resistance values of the variable resistive elements based on the detected differential voltage amplitude. By adjusting these resistance parameters, the system can optimize the balance between bandwidth expansion and group delay characteristics. The control circuit modifies the resistance parameters to achieve desired frequency response characteristics without excessive group delay degradation.
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 suppresses distortion and expands the gain band to high frequencies while minimizing group delay degradation, improving the overall performance of the optical receiving circuit.
Implementation Method 1
a first inductor, a second inductor, a first variable resistive element, and a second variable resistive element. The first inductor is electrically connected between the first input terminal and the first node, the second inductor is electrically connected between the second input terminal and the second node
Implementation Method 2
a first variable resistive element, and a second variable resistive element. The first variable resistive element is electrically connected between the first node and the second input terminal, and the second variable resistive element is electrically connected between the second node and the first input terminal
Data Source
AI summary
A receiving circuit includes a first input terminal and a second input terminal, an input circuit that includes a first node, a second node, a first inductor, a second inductor, a first variable resistive element, and a second variable resistive element. The first variable resistive element is electrically connected between the first node and the second input terminal, and the second variable resistive element is electrically connected between the second node and the first input terminal. The receiving circuit further includes a differential amplifier configured to generate a differential voltage signal in accordance with a differential current signal. The receiving circuit still further includes a control circuit configured to perform detection of an amplitude of the differential voltage signal and change a resistance value of the first variable resistive element and a resistance value of the second variable resistive element based on a result of the detection.