TIA Supply Voltage Feedback for Stable DC Output Linearity
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Solution Overview
Problem
Trans-impedance amplifiers (TIAs) in high-speed fiber optic communication systems face challenges in maintaining stable and linear output voltage, as they are susceptible to variations due to process, voltage, and temperature changes, leading to non-linearity and significant DC voltage drops across feedback resistors, which affect the accuracy of the signal conversion.
Innovation Solution
The implementation of a Low-Dropout Voltage Regulator (LDO) circuit that adjusts the supply voltage based on the DC output voltage of the TIA, using an operational amplifier to compare the output voltage against a reference voltage and provide common-mode feedback to regulate the supply voltage, thereby reducing the DC voltage drop and maintaining linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a TIA is used in high-speed fiber optic communication systems, then signal conversion is achieved, but the output voltage becomes susceptible to variations due to process, voltage, and temperature changes
Solution Approach 1:
The patent implements a feedback mechanism where the LDO circuit monitors the DC output voltage of the TIA and adjusts the supply voltage accordingly. The operational amplifier compares the output voltage against a reference voltage and provides common-mode feedback to regulate the supply voltage, thereby compensating for PVT variations and stabilizing the output voltage.
Solution Approach 2:
The patent dynamically adjusts the supply voltage parameter to counteract the effects of process, voltage, and temperature variations. By changing the supply voltage through the LDO circuit based on real-time output voltage conditions, the system maintains stable TIA performance despite environmental changes.
2Measurement precision
If the TIA operates with standard supply voltage regulation, then power consumption is maintained, but significant DC voltage drops occur across feedback resistors affecting signal accuracy
Solution Approach 1:
The LDO circuit acts as an intermediary between the power supply and the TIA, providing a regulated supply voltage that compensates for voltage drops across feedback resistors. This intermediary regulation ensures that the TIA receives a stable voltage, improving signal conversion accuracy without significantly increasing power consumption.
3Reliability
If the LDO circuit regulates a large portion of the supply DC current, then output voltage stability is improved, but device complexity and power consumption increase
Solution Approach 1:
The LDO circuit is designed to regulate only a portion of the total supply DC current required by the TIA, rather than attempting to regulate the entire current. This partial regulation approach provides sufficient output voltage stability to compensate for PVT variations while avoiding the excessive complexity and power consumption that would result from regulating 100% of the supply current.
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 solution effectively stabilizes the TIA's output voltage, reducing its susceptibility to process, voltage, and temperature variations, and enhances the linearity of the transimpedance amplification process, ensuring accurate signal conversion and improved power supply rejection ratio.
Implementation Method 1
The LDO circuit is configured to adjust the supply voltage responsive to a DC voltage at an output of the TIA
Implementation Method 2
The LDO circuit is configured to adjust the supply voltage to lessen variations of the DC voltage at an output of the TIA
Data Source
AI summary
An apparatus, such as a coherent optical receiver, includes a trans-impedance amplifier (TIA) and a low dropout (LDO) voltage regulator circuit for providing a supply voltage to the TIA. The LDO circuit is configured to adjust the supply voltage responsive to a DC voltage at an output of the TIA. In some implementations the LDO circuit may provide only a fraction of a supply current to the TIA, with another fraction provided by a partial current replica source.