Double-Feedback Transimpedance Amplifier for Stable Termination
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Solution Overview
Problem
Existing transimpedance amplifiers (TIAs) face challenges in maintaining correct termination and stable frequency characteristics due to large input resistance variations caused by manufacturing variations, temperature changes, and power supply voltage variations.
Innovation Solution
A transimpedance amplifier configuration with a reduced input resistance is implemented, featuring a double feedback loop that includes feedback to the source or emitter of the first transistor, along with an inverting amplifier circuit and multiple current-voltage and voltage-current conversion circuits to stabilize the input terminal voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the input resistance value of the TIA is large, then the TIA can convert current signal to voltage signal with high gain, but the fluctuation range of the input resistance value due to manufacturing variations becomes large, causing incorrect termination and frequency characteristic fluctuations
Solution Approach 1:
The patent changes the input resistance parameter from a large value to a small value (reduced input resistance). This parameter change reduces the fluctuation range due to manufacturing variations while maintaining correct termination through the feedback mechanism, thereby resolving the contradiction between gain and manufacturing precision.
Solution Approach 2:
The patent introduces a feedback mechanism where a feedback current is applied to the input terminal based on the output signal. This feedback stabilizes the input terminal voltage and compensates for manufacturing variations, allowing the system to maintain correct termination and stable frequency characteristics even with reduced input resistance.
2Reliability
If the input resistance value of the TIA is large, then the TIA can operate with high impedance, but the TIA is not correctly terminated and frequency characteristics fluctuate
Solution Approach 1:
The feedback mechanism stabilizes the input terminal voltage by applying a feedback current that compensates for variations. This ensures correct termination is maintained regardless of input resistance value, thereby improving reliability and frequency characteristic stability simultaneously.
Solution Approach 2:
By changing the input resistance to a reduced value, the system achieves better termination accuracy. The feedback mechanism then maintains frequency characteristic stability by compensating for any remaining variations, resolving the contradiction between termination accuracy and frequency stability.
Data Source
AI summary
A transimpedance amplifier includes an input terminal, a first transistor having a source connected to the input terminal, a first current-voltage conversion circuit, a first voltage-current conversion circuit and a second voltage-current conversion circuit that convert a voltage corresponding to an output voltage of the first current-voltage conversion circuit into a current, an inverting amplifier circuit having an input node connected to the source or the emitter of the first transistor and an output node connected to a gate or a base of the first transistor, a second current-voltage conversion circuit that converts an output current of the second voltage-current conversion circuit into a voltage, and an output terminal that outputs the voltage converted by the second current-voltage conversion circuit, wherein the output current of the first voltage-current conversion circuit is fed back to the source or the emitter of the first transistor.