MOS Leakage Compensation Circuit With Replica Current Tracking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing leakage-current compensation circuits have performance shortcomings, particularly in terms of accuracy and suitability for new technologies with limited voltage headroom, due to increased gate-tunneling effects in MOS devices like MOSFETs and MOS capacitors, which affect circuit performance in applications such as PLL loop filters and VCO tuning varactors.
Innovation Solution
A leakage-current compensation circuit is implemented using a current mirror and differential amplifier to track and cancel out leakage currents in MOS devices by creating a proportional relationship between a target component and a replica component, with AC coupling to accurately compensate for both DC and AC components of the leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If MOS device gate thickness is reduced to scale down technology size, then device integration density is improved, but gate-tunneling leakage current increases
Solution Approach 1:
The patent creates a replica MOS device that copies the electrical characteristics of the target MOS device, including its leakage current behavior. The replica device is configured to generate a compensation current that mirrors the target device's leakage current, allowing accurate cancellation of the harmful leakage effect while maintaining the benefits of scaled-down device dimensions.
2Reliability
If conventional leakage compensation circuits are used, then some leakage current compensation is achieved, but compensation accuracy is insufficient and voltage headroom is excessive
Solution Approach 1:
The patent implements a feedback mechanism where the replica MOS device continuously monitors the target device's operating conditions and adjusts its compensation current accordingly. The compensation current is dynamically adjusted based on the target device's instantaneous leakage current, ensuring high compensation accuracy while operating within limited voltage headroom constraints through intelligent current control.
Solution Approach 2:
The patent changes the operating parameters of the compensation circuit by using current-mode operation instead of voltage-mode operation. This parameter change allows the circuit to achieve accurate leakage compensation with reduced voltage headroom requirements, as the compensation is achieved through current mirroring and subtraction rather than voltage regulation.
3Measurement precision
If AC coupling is added to track both AC and DC components of potential difference, then compensation accuracy is improved, but circuit complexity increases
Solution Approach 1:
The patent merges the AC coupling functionality directly into the replica MOS device configuration by coupling the gate of the replica device to the gate of the target device through an AC coupling capacitor. This integration allows the replica device to automatically track both AC and DC components of the target device's gate potential, achieving high compensation accuracy without adding separate complex tracking circuits.
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 compensation circuit effectively cancels out leakage currents, improving circuit performance by reducing phase offsets and noise contributions, especially in RF applications, by ensuring the compensation current accurately matches and opposes the leakage current.
Implementation Method 1
MOS (metal oxide semiconductor) devices suffer from gate leakage due to a gate-tunneling effect
Implementation Method 2
An AC coupling may be provided to superimpose an AC-component of the first potential difference on the second potential difference
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A leakage-current compensation circuit, comprising: a first node for connection of a first component thereto, whereby a first leakage current flows through the first component and through the first node with a given polarity with respect to the first node, the magnitude of the first leakage current dependent on a first potential difference across the first component; a second component connected to a second node and configured such that a second leakage current flows through the second component and through the second node, the magnitude of the second leakage current dependent on a second potential difference across the second component; a current mirror connected to the first node and the second node and configured to cause a compensation current to flow through the first node with opposite polarity to the first leakage current with respect to the first node, the magnitude of the compensation current dependent on the magnitude of the second leakage current due to current mirroring; a differential amplifier configured, based on a difference between the first potential difference and the second potential difference, to control a feedback component connected in series with the second component along a current path carrying the second leakage current to cause the second potential difference to track the first potential difference; and an AC coupling connected to superimpose an AC-component of the first potential difference on the second potential difference.