Transimpedance Amplifier Replica Feedback for High-Rate Linearity
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Solution Overview
Problem
Prior art transimpedance amplifiers suffer from increased non-linearity and distortion at higher data rates, limiting their effectiveness in high-speed applications.
Innovation Solution
The implementation of a transimpedance amplifier with a feedback loop and a replica circuit that adjusts degeneration resistance in relation to feedback resistance, using a FET switch and current mirror to maintain linearity and stability, and a divider element to reduce the effect of switch resistance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If prior art amplifiers are used at higher data rates, then data transmission speed increases, but non-linearity and distortion increase
Solution Approach 1:
The patent implements dynamic adjustment of the degeneration resistance in the amplifier circuit. A replica circuit continuously monitors the feedback resistance and automatically adjusts the degeneration resistance to maintain optimal linearity as data rates change. This dynamic adaptation allows the amplifier to maintain high linearity performance across varying speeds from 10 Gbps to 100 Gbps and beyond.
Solution Approach 2:
The patent employs a feedback mechanism where a replica circuit monitors the main amplifier's feedback resistance and uses this information to control the degeneration resistance. The replica circuit creates a feedback loop that automatically adjusts circuit parameters to compensate for non-linearity and distortion, ensuring reliable operation at high data rates.
2Power
If feedback resistance is increased to improve gain, then amplifier gain improves, but stability and linearity deteriorate
Solution Approach 1:
The patent introduces a degeneration resistance as an intermediary element between the feedback path and the amplifier input. This intermediate component acts as a buffer that stabilizes the amplifier operation by providing local feedback, thereby maintaining stability and linearity even when the main feedback resistance is increased to achieve higher gain.
Solution Approach 2:
The patent dynamically changes the degeneration resistance parameter based on the feedback resistance value. As the feedback resistance changes to adjust gain, the degeneration resistance is simultaneously adjusted to maintain optimal stability and linearity. This coordinated parameter adjustment allows the amplifier to achieve high gain without sacrificing stability.
3Reliability
If degeneration resistance is adjusted to maintain linearity, then linearity improves, but circuit complexity increases
Solution Approach 1:
The patent uses a replica circuit that is a simplified copy of the main amplifier circuit. This replica circuit replicates the essential feedback path and resistance characteristics, allowing it to generate control signals for the degeneration resistance adjustment. By using a copied version rather than a complex control system, the solution maintains linearity while minimizing additional circuit complexity.
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 enhances the dynamic range, linearity, and stability of the amplifier, enabling support for data rates of 10 gigabit per second or greater while minimizing distortion and peaking.
Implementation Method 1
A current mirror may be part of the replica circuit feedback loop
Implementation Method 2
The amplifier feedback loop may further comprise a FET switch configured to receive the control signal
Data Source
AI summary
Various amplifier configurations having increased bandwidth, linearity, dynamic range, and less distortion are shown and disclosed. To increase bandwidth in a transimpedance amplifier, a replica circuit is created to replicate a degeneration resistance, or the resistance or value that relates to a feedback resistance. From the replica circuit, the replicated values are mirrored and processed to control a FET switch which modifies a degeneration resistance. The FET switch control signal is related to the feedback resistance and modifies the degeneration resistance to thereby maintain the product of the feedback resistance and the degeneration resistance as a constant. In another embodiment, a second switch controlled by an automatic gain control signal is established between a first stage amplifier and a second stage amplifier to improve dynamic range and bandwidth without degrading other amplifier specifications.