Burst Transimpedance Amplifier With Internal Reset Time-Constant Switching
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Solution Overview
Problem
Existing burst transimpedance amplifiers (BTIAs) face challenges in managing response performance and consecutive identical code tolerance simultaneously, particularly in optical receivers used for passive optical networks (PONs) like fiber to the home (FTTH).
Innovation Solution
A transimpedance amplifier circuit that generates a reset signal internally, using a comparator to compare the collector voltage of a transistor with a reference voltage, allowing for dynamic adjustment of time constants to enhance both response speed and code tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the time constant is made small to achieve high speed response, then the response speed is improved, but the consecutive identical code tolerance deteriorates
Solution Approach 1:
The patent applies dynamics by making the time constant adjustable rather than fixed. The time constant switching circuit changes the time constant value based on the reset signal: using a small time constant during burst periods for high-speed response, and a large time constant during no-signal periods to enhance consecutive identical code tolerance. This dynamic adjustment resolves the contradiction between response speed and code tolerance.
2Reliability
If the time constant is made large to enhance consecutive identical code tolerance, then the code tolerance is improved, but the response speed deteriorates
Solution Approach 1:
The patent uses dynamic time constant adjustment where the time constant is set large during no-signal periods to enhance consecutive identical code tolerance, and switched to small during burst periods to maintain high response speed. The time constant switching circuit enables this dynamic behavior, allowing the system to optimize for code tolerance when no signal is present while maintaining fast response when signals arrive.
3Speed
If an external reset signal is used to switch time constants, then the response performance and code tolerance are improved, but the device complexity increases
Solution Approach 1:
The patent applies self-service by enabling the BTIA to generate its own reset signal internally rather than requiring an external reset signal from the MAC-LSI. The reset signal generation circuit detects the no-signal period and generates the reset signal autonomously, which is then used by the time constant switching circuit. This self-generated reset signal approach reduces device complexity and improves versatility while maintaining the ability to switch time constants for optimized performance.
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 enables the BTIA to achieve high-speed response and improved consecutive identical code tolerance, thereby enhancing the overall performance of optical receivers in PONs without the need for external reset signals.
Implementation Method 1
a comparator configured to compare a collector voltage of the transistor with a reference voltage and output a reset signal
Implementation Method 2
a TIA applied to a passive optical network (PON) used in fiber to the home (FTTH) or the like is referred to as a burst TIA (BTIA)... an optical signal is converted into a current signal by a light receiving element such as a photo diode (hereinafter abbreviated as PD); thereafter, the current signal is converted into a voltage signal
Data Source
AI summary
A reset signal is generated by a TIA circuit alone. In an embodiment, a transimpedance amplifier configured to convert a current signal into a voltage signal includes a transimpedance stage including an amplification stage constituted of a transistor with a grounded emitter, and a comparator configured to compare a collector voltage of the transistor with a reference voltage and output a reset signal.