Current-Voltage Converter with Twin-Circuit Error Current Compensation
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Solution Overview
Problem
Current-voltage converters in high-fidelity amplifiers face challenges in maintaining low distortion due to error currents induced by transistors in common gate or base stages, particularly when integrated into circuits, where substrate current absorption is difficult to measure and ESD protections contribute to additional losses.
Innovation Solution
A current-voltage converter design featuring a twin circuit with a voltage follower and current reinjection means, including a current mirror circuit, to compensate for error currents and substrate absorption, ensuring minimal distortion and compatibility with both discrete and integrated circuit forms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If common gate or base stages are used in the current-voltage converter, then the converter can operate in open loop and maintain constant current and voltage for optimal DAC performance, but error currents are induced which degrade the digital signal quality
Solution Approach 1:
The patent measures the error currents generated by the common gate/base stages and reinjects them with opposite polarity to cancel their harmful effects. The harmful error currents are converted into a measurable signal that, when inverted and added back, neutralizes their distortion impact on the DAC output.
Solution Approach 2:
The patent implements a feedback mechanism where error currents are measured by dedicated measurement circuits, processed through operational amplifiers, and reinjected into the signal path. This closed-loop feedback system continuously compensates for the error currents generated by the transistors in the common gate/base stages.
2Productivity
If the current-voltage converter is produced as an integrated circuit, then production efficiency and compactness are improved, but substrate current absorption becomes difficult to measure and ESD protections cause additional current losses
Solution Approach 1:
The patent introduces twin circuits as intermediary measurement paths that duplicate the signal flow through identical transistor structures. These twin circuits serve as mediators to measure the substrate current absorption and ESD protection currents without disrupting the main signal path, enabling quantification of the integrated circuit's parasitic losses.
Solution Approach 2:
The patent measures and compensates for substrate current absorption by changing the operational parameters of the twin circuits to match the main circuit conditions. By adjusting the twin circuit operating points to reflect actual substrate current draw and ESD protection activation levels, the system dynamically compensates for these integrated circuit-specific losses.
3Reliability
If ESD protections are added to protect integrated circuit components, then reliability against electrostatic discharge is improved, but additional current absorption occurs which degrades signal quality
Solution Approach 1:
The patent measures the current absorbed by ESD protection structures and reinjects it with opposite polarity to cancel the harmful current sink effect. The ESD protections, which normally only cause signal degradation, become compensatable elements through the measurement and reinjection mechanism, converting their harmful current absorption into a correctable parameter.
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
The solution effectively maintains low harmonic distortion and improves signal quality by compensating for error currents and substrate losses, achieving a distortion gain of 15 to 20 dB, while ensuring optimal operation of current sources in high-fidelity amplifiers.
Implementation Method 1
the reinjection means comprise means for measuring the current at the output of the voltage follower, the said means for measuring the current comprising a current mirror circuit
Implementation Method 2
The error currents are notably due to the currents absorbed in the gates of the transistors of the common base or gate stages
Data Source
Figure 1~2
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AI summary
The current-to-voltage converter (22) comprises: - an input (24) for the current to be converted; - an output (26) for the converted voltage; - a current-to-voltage conversion resistor (36) arranged between the output (26) and a reference potential, - a processing circuit (40) comprising a transistor (60), the input (24) being connected to the output (26) via the transistor (60), - a twin circuit (46) comprising components identical to and disposed in a similar way to those of the processing circuit (40), - a voltage follower (50) connected at the input to the processing circuit (40) and at the output to the twin circuit (46), and - means (51) for reinjecting the current at the output of the follower (50) into the processing circuit (40).