Differential TIA Receiver Circuit for Stable Gain and Frequency Response
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Solution Overview
Problem
Existing receiver circuits face challenges in maintaining stable frequency characteristics when varying gain, leading to signal distortion in digital coherent optical transmission systems.
Innovation Solution
A receiver circuit design that includes a constant current circuit, current splitter circuit, load circuit, and differential transimpedance amplifier circuit, where average voltages are set equivalent across output nodes and terminals to stabilize the operating point and reduce frequency characteristic fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If gain is varied in a receiver circuit, then signal amplification is adjusted, but frequency characteristics fluctuate causing signal distortion
Solution Approach 1:
The patent applies equipotentiality by setting the average voltages of the first output node, second output node, first output terminal, and second output terminal to be equivalent to each other. This creates a balanced operating point that remains stable during gain variations, preventing frequency characteristic fluctuations and signal distortion while allowing gain adjustment.
2Power
If the operating point deviates from optimum, then gain can be increased, but frequency characteristics deteriorate
Solution Approach 1:
By configuring the circuit such that average voltages at all output nodes and terminals are equivalent, the patent maintains the operating point at the optimum position even when gain is adjusted. This prevents frequency characteristic deterioration while achieving the desired gain increase.
3Reliability
If circuit components are added to stabilize operating point, then frequency characteristics improve, but device complexity increases
Solution Approach 1:
The patent achieves frequency characteristic stabilization by configuring existing circuit components to have equivalent average voltages at their output nodes and terminals. This multi-functional approach uses the same circuit elements for both signal processing and operating point stabilization, avoiding additional complexity while improving reliability.
Data Source
AI summary
A receiver circuit includes: a constant current circuit to generate second paired current signals according to first paired current signals; a current splitter circuit to output third paired current signals generated from the second paired current signals, from a first output node and a second output node; and a differential TIA circuit to output paired voltage signals from a first output terminal and a second output terminal, according to the third paired current signals input from a third input node and a fourth input node. The differential TIA circuit includes a first feedback resistor element connected between the third input node and the second output terminal, and a second feedback resistor element connected between the fourth input node and the first output terminal. Average voltages of the first and second output nodes and the first and second output terminals are set to be equivalent to each other.