Current Mirror Filter With Leakage-Independent Low Bandwidth
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Solution Overview
Problem
Current filters in current mirror circuits face issues with leakage current affecting the accuracy of mirror current due to high resistance values needed for low-frequency noise rejection, leading to voltage drops and errors.
Innovation Solution
A current filter circuit with a low pass filter and impedance reduction circuit is introduced, where the low pass filter is coupled between the drain of the source transistor and the reference voltage terminal, and the impedance reduction circuit reduces the bandwidth by using transistors or resistors, minimizing the impact of gate leakage on output current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If high resistance value is used in the current filter to reject low frequency noise, then noise rejection is improved, but voltage drops due to gate leakage increase causing errors in mirror current
Solution Approach 1:
A low pass filter is introduced as an intermediary component between the current source and the current mirror circuit. This filter selectively attenuates noise signals while allowing the DC component to pass through, thereby reducing noise without requiring high resistance values that would cause leakage-induced voltage drops and current errors.
Solution Approach 2:
The patent changes the resistance value parameter in the filter circuit from high resistance to optimized lower resistance values. By combining this with capacitance selection, the filter achieves effective noise rejection at low frequencies without the adverse effects of high resistance, thus maintaining mirror current accuracy while improving noise rejection.
2Object-affected harmful factors
If high resistance is used in the filter, then low frequency noise rejection is improved, but bandwidth of the filter increases
Solution Approach 1:
The patent optimizes the resistance and capacitance parameters of the low pass filter to achieve the desired noise rejection performance. By carefully selecting component values, the filter provides effective low frequency noise attenuation while maintaining a bandwidth that is appropriate for the application, avoiding both excessive bandwidth and the need for high resistance values.
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 filters noise in current mirror circuits without causing errors in mirror current, achieving leakage-independent mirroring and reduced bandwidth, thereby improving the accuracy and reliability of current filtering.
Implementation Method 1
A current filter circuit with a low pass filter and impedance reduction circuit is introduced, where the low pass filter is coupled between the drain of the source transistor and the reference voltage terminal
Implementation Method 2
an impedance reduction circuit is coupled to the current filter circuit for reducing bandwidth of the current filter circuit
Data Source
AI summary
A current filter circuit is provided. The current filter circuit comprises a source transistor comprising a drain, a gate, and a source. The source of the source transistor is coupled to a reference voltage terminal, the gate of the source transistor is coupled to the gate of a mirror transistor, and the drain of the source transistor is coupled to a reference current source. The mirror transistor comprises a drain, a gate, and a source. The source of the mirror transistor is coupled to the reference voltage terminal, the gate is coupled to the gate of the source transistor, and the drain is coupled to a load. The current filter circuit comprises a low pass filter for filtering noise. The current filter circuit also comprises an impedance reduction circuit coupled to the drain of the mirror transistor for reducing bandwidth of the current filter circuit.