Programmable Transconductor Tuning for Impedance-Accurate Measurement
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Solution Overview
Problem
Transconductance amplifiers lack programmability, which affects the accuracy of voltage measurements in parametric measurement units and other devices due to external impedance variations, such as those from conductors or connectors.
Innovation Solution
A programmable transconductor circuit that includes a resistor, a programmable impedance circuit, an amplifier, and a current mirror, allowing for digital tuning to adjust the transconductance based on a tuning code, enabling linear proportional output current adjustment in response to input voltage and impedance variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a traditional transconductance amplifier is used, then the circuit is simple and fixed, but it lacks programmability and cannot compensate for external impedance variations
Solution Approach 1:
The patent implements a programmable transconductor where the transconductance value can be dynamically adjusted through digital control signals. The circuit uses switchable resistor networks and controllable current sources that allow the transconductance parameter to be changed in real-time based on external impedance conditions, transforming a static circuit into an adaptive one.
Solution Approach 2:
The invention changes the operational parameters of the transconductance amplifier by introducing programmable resistance values and controllable current magnitudes. Through digital control, the circuit can switch between different resistance configurations and current levels, enabling adaptation to varying external impedance without requiring a complete circuit redesign.
2Measurement precision
If external impedance variations are present, then measurement accuracy deteriorates, but adding programmability increases device complexity
Solution Approach 1:
The patent incorporates feedback mechanisms where the circuit monitors external impedance conditions and automatically adjusts its transconductance parameter to compensate. The programmable transconductor uses control logic that responds to impedance variations by modifying its operation, creating a closed-loop system that maintains measurement accuracy despite external disturbances.
Solution Approach 2:
The invention introduces a programmable control interface as an intermediary between the transconductance amplifier and external impedance variations. This control layer processes impedance information and translates it into appropriate transconductance adjustments, shielding the core measurement function from direct exposure to external variations while maintaining accuracy.
3Adaptability or versatility
If the transconductance is fixed, then the device is easier to manufacture, but it cannot be tuned for different measurement conditions
Solution Approach 1:
The patent divides the transconductance control into discrete segments or steps through switchable resistor networks and quantized current sources. Instead of requiring continuous analog adjustment, the circuit uses segmented control elements that can be independently switched, simplifying manufacturing while providing multiple tunable states for different measurement conditions.
Data Source
AI summary
In examples, a circuit includes a first and second resistors, a programmable impedance circuit, an amplifier, and a current mirror. The first resistor has a first terminal coupled to a VIN terminal, and a second terminal. The second resistor has a first terminal coupled to the second terminal of the first resistor, and a second terminal coupled to a ground terminal. The programmable impedance circuit has a first terminal coupled to the second terminal of the first resistor, a tuning input, and a third terminal. The amplifier has an inverting input coupled to the ground terminal, a non-inverting input coupled to the third terminal of the programmable impedance circuit, and an output terminal. The current mirror has a first terminal coupled to the output terminal of the amplifier, a second terminal coupled to the third terminal of the programmable impedance circuit, and a third terminal coupled to an IOUT terminal.