Photodiode-TIA Flip-Chip Receiver for Wire-Bond Inductance Limits
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Solution Overview
Problem
In high-frequency applications, prior art photodiode and transimpedance amplifier circuits suffer from inductance issues due to wire bond connections, leading to overshoot, ringing, and reduced bandwidth, as well as suboptimal performance from long ground paths and floating grounds.
Innovation Solution
A flip chip configuration is used to integrate the photodiode and transimpedance amplifier on the same semiconductor die, eliminating wire bonds and establishing a common ground node, with a coplanar waveguide formed by a ground plane surrounding the transmission line interconnect, and capacitors connected between the bias voltage node and ground to improve signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wire bonds are used to connect the photodiode to the transimpedance amplifier, then the circuit can be assembled using conventional bonding techniques, but inductance is introduced which causes overshoot, ringing and loss of energy at high frequency
Solution Approach 1:
The patent merges the photodiode and transimpedance amplifier onto a single semiconductor die, eliminating the need for wire bonds between these components. This integration removes the inductive effects caused by wire bonds while maintaining manufacturability through standard semiconductor fabrication processes.
Solution Approach 2:
The patent extracts and eliminates the wire bond interconnect from the signal path between the photodiode and transimpedance amplifier. By removing this inductive element, the circuit achieves superior high-frequency performance without requiring alternative bonding techniques.
2Adaptability or versatility
If the photodiode and transimpedance amplifier are located on separate integrated circuit dies, then the components can be manufactured independently, but long ground paths and floating grounds result in suboptimal circuit performance
Solution Approach 1:
The patent combines the photodiode and transimpedance amplifier on a single semiconductor die, which eliminates long ground paths and floating ground issues. This integration ensures a common ground reference between components while maintaining the ability to manufacture the entire device using standard semiconductor fabrication processes.
3Ease of operation
If wire bonds connect the TIA to the package, then electrical connection to the circuit board can be established, but the wire bond arrangement introduces inductance that limits bandwidth at high frequencies
Solution Approach 1:
The patent extracts and eliminates wire bonds from the signal path between the photodiode and transimpedance amplifier. By removing this inductive interconnect, the circuit achieves extended bandwidth and improved high-frequency response while maintaining electrical connection capabilities through integrated semiconductor contacts.
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 significantly reduces inductance, shortens ground connections, and enhances high-frequency performance by providing a stable, direct ground path and improved signal processing, particularly beneficial for pulse amplitude modulation (PAM4) signals.
Implementation Method 1
a photodiode, integrated on a substrate, configured to receive an optical signal and generate an electrical current representing the optical signal
Implementation Method 2
the ground plane surrounding the transmission line interconnect between the photodiode and the transimpedance amplifier create a coplanar waveguide
Data Source
AI summary
A transimpedance amplifier and photodiode that has a bias voltage node established at a bias voltage and a ground node/plane that connects, over a short distance as compared to the prior art, to a photodiode and a transimpedance amplifier. The photodiode is in a substrate and configured to receive and convert an optical signal to an electrical current. The photodiode has an anode terminal and a cathode terminal which is connected to the bias voltage node. One or more capacitors in or on the substrate and connected between the bias node and the ground node. The transimpedance amplifier has an input connected to the anode terminal of the photodiode and an output that presents a voltage representing the optical signal to an output path. The transimpedance amplifier and the photodiode are both electrically connected in a flip chip configuration and the ground plane creates a coplanar waveguide.