RF Switch FET Body Biasing With Diode Paths for GIDL Control
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Solution Overview
Problem
Existing RF switch stacks experience undesired gate-induced drain/body leakage current (GIDL) during OFF state, leading to de-biasing effects, early transistor breakdown, and increased complexity in bias generator design.
Innovation Solution
The implementation of diode stacks across the body resistor ladder in RF switch stacks, which generate discharge paths for the GIDL current during RF signal swings, thereby mitigating the de-biasing effect and reducing the complexity of the bias generator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a body resistor ladder is used to bias the FET switch stack, then the transistors can be biased during operation, but gate-induced drain/body leakage current (GIDL) flows through the body resistor ladder causing de-biasing effects and early transistor breakdown
Solution Approach 1:
The patent extracts the harmful GIDL current from the main biasing path by introducing a separate leakage current path. Diode stacks are connected between body resistor ladder nodes and ground to provide a dedicated route for GIDL current to discharge, preventing it from flowing through the body resistor ladder and causing de-biasing effects.
Solution Approach 2:
The diode stacks act as intermediary elements between the body resistor ladder and ground. These diodes are strategically placed to intercept GIDL current at specific nodes, serving as mediators that redirect the harmful current away from the transistor bodies and toward ground, thereby protecting the transistors from breakdown.
2Device complexity
If the GIDL current is allowed to flow through the body resistor ladder, then the circuit remains simple, but the DC voltage distribution across the body resistor ladder is modified causing de-biasing effects
Solution Approach 1:
The patent segments the body resistor ladder into multiple sections with diode stacks placed at specific nodes. This segmentation allows the GIDL current to be intercepted and discharged at localized points rather than flowing through the entire ladder, maintaining stable DC voltage distribution across each segment while keeping the overall circuit relatively simple.
Solution Approach 2:
The diode stacks provide preliminary anti-action by preemptively capturing the GIDL current before it can disrupt the DC voltage distribution. By placing diodes at strategic nodes, the circuit proactively counteracts the harmful effect of GIDL current, preventing de-biasing effects before they occur.
3Reliability
If more negative biasing voltage is applied to improve linearity performance in OFF state, then linearity improves, but the biasing circuit becomes more complex and occupies larger area
Solution Approach 1:
The patent converts the harmful GIDL current into a beneficial element by using it to charge the body capacitances during RF signal swings. The diode stacks allow controlled discharge of this current, transforming what was previously a harmful leakage current into a useful charge pump mechanism that maintains proper body bias voltages without requiring additional complex biasing circuits.
Solution Approach 2:
The body resistor ladder and diode stacks work together in a self-service manner where the GIDL current, instead of requiring external compensation circuits, is utilized to automatically maintain the body bias voltages. The diode stacks enable the circuit to self-regulate the body potentials using the inherently present leakage current, eliminating the need for more complex and area-consuming biasing solutions.
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
This solution effectively reduces the negative impacts of GIDL current, maintaining a proper voltage distribution across the stack, preventing early voltage breakdown, and allowing for a simpler, more compact biasing circuit without compromising power handling or linearity performance.
Implementation Method 1
The implementation of diode stacks across the body resistor ladder in RF switch stacks, which generate discharge paths for the GIDL current during RF signal swings
Data Source
AI summary
Methods and devices to reduce gate induced drain leakage current in RF switch stacks are disclosed. The described devices utilize multiple discharge paths and/or less negative body bias voltages without compromising non-linear performance and power handling capability of power switches. Moreover, more compact bias voltage generation circuits with smaller footprint can be implemented as part of the disclosed devices.