Expanded Shunt Current Source With Feedback for Fast Stable Response
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Solution Overview
Problem
Conventional current sources in test and measurement systems respond slowly to changes in source voltage when the load resistance is larger than the source resistance, leading to reduced speed and stability, and increasing power dissipation with larger source resistances.
Innovation Solution
Employing a gain component with attenuator feedback to maintain constant gain at lower frequencies and reduce gain at higher frequencies, along with an inductor in series with the source resistor, to make a lower resistance 'look' larger, allowing higher current generation at higher frequencies without increased power dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the source resistance is increased to improve current source speed when load resistance is larger than source resistance, then the response speed improves, but the power dissipation increases
Solution Approach 1:
The patent introduces an operational amplifier as an intermediary component between the voltage source and source resistance. The op-amp with high gain allows a smaller source resistance to effectively behave as a larger resistance, thereby improving response speed without increasing power dissipation in the source resistance
2Speed
If an operational amplifier with large gain is used to make the source resistance appear larger, then the response speed improves, but the stability deteriorates due to gain roll-off at low frequencies
Solution Approach 1:
The patent modifies the effective resistance parameter by using an op-amp to create an apparent resistance that is larger than the physical source resistance. This parameter transformation allows the system to achieve fast response characteristics of high resistance while maintaining the low power dissipation of low resistance
3Loss of energy
If the source resistance is made smaller to reduce power dissipation, then the power consumption decreases, but the response speed deteriorates when load resistance is larger than source resistance
Solution Approach 1:
The operational amplifier serves as a mediator that decouples the relationship between source resistance value and response speed. By using the op-amp's high gain, the system achieves fast response without requiring large source resistance, thus maintaining low power dissipation
Data Source
AI summary
A current source has at least one gain component having a constant gain at frequencies below a frequency point, and having a gain inversely proportional to frequency at frequencies above the frequency point, the gain component having an input and an output, a source resistor connected in series with the output of the gain component, the gain component to regulate a voltage across the source resistor to be a source voltage, such that the gain of the gain component limits regulation by the gain component of the source voltage and an output voltage across a load between a high terminal and a low terminal, and a feedback component to receive at least a portion of the output voltage, the feedback component connected to the input of the gain component, the feedback component configured to reduce the gain of the gain component available to regulate the source voltage across the source resistor.