Transimpedance Amplifier Feedback Control for High-Speed Linearity
Find Innovative SolutionsGenerate Solutions
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 and failing to maintain linearity across varying input currents.
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 control gain and maintain constant product of degeneration and feedback resistances, thereby reducing distortion and improving linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If prior art amplifiers are used at higher data rates, then productivity increases, but linearity deteriorates and distortion increases
Solution Approach 1:
The patent implements a feedback mechanism where a replica circuit mirrors the main amplifier's feedback resistance changes and uses this information to dynamically adjust the degeneration resistance. This feedback loop ensures that as feedback resistance varies with data rate, the degeneration resistance compensates proportionally, maintaining constant linearity across all operating conditions.
Solution Approach 2:
The patent dynamically changes the degeneration resistance parameter in proportion to the feedback resistance parameter. By maintaining a constant ratio between these two parameters through the replica circuit, the system adapts to different data rates while preserving linearity, effectively transforming a static parameter into a dynamically optimized one.
2Power
If feedback resistance is increased to improve gain, then power increases, but distortion increases at higher data rates
Solution Approach 1:
The replica circuit continuously monitors feedback resistance changes and provides feedback control to the degeneration resistance adjustment mechanism. This ensures that gain enhancement through increased feedback resistance is automatically compensated by proportional degeneration resistance increases, preventing distortion at higher data rates.
Solution Approach 2:
The patent creates a composite resistance control system combining the main feedback resistance path with a replica-based degeneration resistance control path. This composite approach integrates two resistance control mechanisms that work together to simultaneously achieve high gain and low distortion through coordinated parameter adjustment.
3Object-generated harmful factors
If degeneration resistance is increased to reduce distortion, then gain decreases
Solution Approach 1:
The patent transforms the degeneration resistance from a static component into a dynamic parameter that automatically adjusts in proportion to feedback resistance changes. Through the replica circuit, the degeneration resistance dynamically tracks feedback resistance variations, ensuring that distortion reduction and gain maintenance are achieved simultaneously through coordinated parameter changes rather than trade-offs.
Solution Approach 2:
The patent implements coordinated parameter changes where both feedback resistance and degeneration resistance are adjusted together in a fixed ratio. This simultaneous parameter adjustment ensures that the beneficial effects of increased degeneration resistance (distortion reduction) are offset by proportional increases in feedback resistance (gain maintenance), eliminating the traditional trade-off.
4Speed
If amplifier bandwidth is increased to support higher data rates, then stability deteriorates due to increased non-linearity
Solution Approach 1:
The replica circuit provides continuous feedback about feedback resistance changes to the degeneration resistance control mechanism. This feedback ensures that as bandwidth increases and data rates rise, the degeneration resistance automatically adjusts to compensate for potential instability, maintaining consistent amplifier behavior across all operating conditions.
Solution Approach 2:
The patent implements coordinated parameter changes between feedback resistance and degeneration resistance that maintain a constant ratio relationship. This proportional parameter adjustment ensures that stability-critical parameters remain in optimal relationship even as bandwidth and data rate parameters increase, preventing the stability deterioration that normally accompanies higher-speed operation.
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.