Shared-Input Cascode Transimpedance Amplifier for Multi-Rate Accuracy
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Solution Overview
Problem
Conventional multi-rate trans-impedance amplifiers face challenges in efficiently switching between different operation rates without affecting other trans-impedance amplifiers, leading to issues with parasitic impedances and capacitances that impact accuracy and precision, especially at high speeds.
Innovation Solution
The integration of two cascode trans-impedance amplifiers with shared input transistive elements and external switches allows for independent enabling and disabling of each amplifier, reducing parasitic effects and improving performance by using distinct resistive elements and cascode coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If switches are placed in series with resistive elements to change impedances for multi-rate operation, then the trans-impedance amplifier can switch between multiple rates, but parasitic impedances and capacitances are introduced that degrade accuracy and precision
Solution Approach 1:
The patent extracts the switching function from the signal path by using switches in the bias circuits of the cascode amplifiers rather than in series with the feedback resistors. This removes the source of parasitic impedances and capacitances from the high-precision measurement path while retaining the ability to change operating rates through bias control.
Solution Approach 2:
The patent introduces bias circuits as intermediary elements that control the operating state of the cascode amplifiers. By mediating the rate switching through bias control rather than direct signal path switching, the system achieves multi-rate operation without introducing parasitic effects into the measurement path.
2Device complexity
If a single trans-impedance amplifier is used for multi-rate conversion, then the circuit complexity is reduced, but the ability to independently optimize performance at different rates is limited
Solution Approach 1:
The patent segments the single trans-impedance amplifier into two parallel cascode amplifier paths, each optimized for different operating rates. The first cascode amplifier is optimized for a first rate while the second is optimized for a second rate, allowing independent optimization without requiring a completely separate amplifier for each rate.
Solution Approach 2:
The patent creates a multi-functional amplifier structure where two cascode amplifiers share common input and output nodes but have independent bias control. This universal structure can operate at multiple rates by selectively enabling or disabling specific amplifier paths through their respective bias circuits.
3Adaptability or versatility
If switches are used to disable trans-impedance amplifiers for rate switching, then multi-rate operation is achieved, but the switches themselves introduce parasitic effects that impact performance
Solution Approach 1:
The patent extracts the switching function from the signal path and places it in the bias control circuits. By removing switches from the high-precision measurement path and relocating them to bias control paths, the harmful parasitic effects are eliminated from the measurement path while retaining switching capability for rate selection.
Data Source
AI summary
Systems and apparatus for converting an input current signal into two or more output voltage signals on an integrated circuit. In one aspect, an integrated circuit includes a first trans-impedance amplifier that includes a first cascode amplifier; and a second trans-impedance amplifier that includes a second cascode amplifier, the second cascode amplifier and the first cascode amplifier sharing an input transistive element; where the first cascode amplifier is coupled to one or more first switches that disable the first trans-impedance amplifier, the second cascode amplifier is coupled to one or more second switches that disable the second trans-impedance amplifier, and control logic coupled to the one or more first switches and the one or more second switches disables at least one of the first trans-impedance amplifier or the second trans-impedance amplifier.