Optical Receiving Circuit Wiring Impedance
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Solution Overview
Problem
The wiring between a photodiode (PD) and a transimpedance amplifier (TIA) in optical receiving circuits causes characteristic deterioration, leading to a degradation in the eye pattern of the voltage signal output.
Innovation Solution
The characteristic impedance of the wiring between the PD and TIA is increased by using narrower and longer anode-side wiring with higher impedance and shorter, wider cathode-side wiring with lower impedance, reducing inductance and improving signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire bonding is used to connect PD and TIA, then electrical power can be supplied and signals transmitted, but characteristic deterioration occurs and eye pattern degrades
Solution Approach 1:
The patent extracts the harmful wiring connections between PD and TIA by implementing flip-chip mounting, which eliminates the need for external wire bonds. The anode and cathode are directly connected through substrate conductors, removing the source of characteristic deterioration and eye pattern degradation caused by traditional wire bonding.
Solution Approach 2:
The substrate serves as an intermediary element that provides direct electrical connection between PD and TIA through conductive patterns. This intermediary structure replaces the problematic wire bonding approach while maintaining electrical connectivity and enabling power supply from TIA to PD.
2Device complexity
If power is supplied from TIA to PD, then number of power sources and pads is reduced, but wiring configuration becomes critical for performance
Solution Approach 1:
The patent segments the wiring into two distinct paths: power supply wiring (cathode connection) and signal wiring (anode connection). This segmentation allows independent optimization of each path - power wiring can be designed for low impedance while signal wiring is optimized for high bandwidth, resolving the conflict between simplified power supply and maintained signal quality.
Solution Approach 2:
Different wiring configurations are applied to different functional requirements: the cathode-side wiring is designed with specific impedance characteristics for power supply, while the anode-side wiring is optimized for signal transmission. This local quality differentiation ensures both power efficiency and signal integrity are achieved simultaneously.
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 enhances the eye opening and reduces jitter in the output signal, resulting in improved optical receiving circuit characteristics.
Implementation Method 1
a photodiode (PD) converts an optical signal into a current signal
Data Source
Figure 1(A)~1(B)
Figure 2(A)~2(B)
Figure 3
AI summary
An optical receiving circuit which suppresses a characteristic deterioration due to a wiring between a PD and a TIA and a method for manufacturing the optical receiving circuit are provided. A optical receiving circuit (300) comprises a photodiode (302), and a transimpedance amplifier (308) that supplies an electrical power source to the photodiode (302). The characteristic impedance of a wiring between the anode of the photodiode (302) and the transimpedance amplifier (308) is higher than the characteristic impedance of a wiring between the cathode of the photodiode (302) and the transimpedance amplifier (308).