Inductive Bias Ladders in RF Switch Stacks for GIDL Control
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Solution Overview
Problem
Field-effect transistor (FET) switch stacks experience undesired gate-induced drain/body leakage current (GIDL) during RF swings, leading to de-biasing effects that result in unbalanced DC voltage distribution and potential early breakdown of transistors, especially those closer to the top of the stack.
Innovation Solution
Incorporating inductive drain and body ladders in RF switch stacks, where inductors are coupled across drain and source terminals and body terminals of FETs to reduce the de-biasing effect by acting as short circuits for DC components and open circuits for AC components of the GIDL current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resistive bias ladders are used in FET switch stacks, then DC voltage distribution can be established, but gate-induced drain/body leakage current causes de-biasing effects leading to unbalanced voltage distribution and potential transistor breakdown
Solution Approach 1:
The patent changes the bias ladder configuration from purely resistive to inductive by introducing inductors in series with the bias lines. This parameter change transforms the bias ladder's impedance characteristics, allowing it to block DC leakage current while maintaining proper RF signal passage and uniform DC voltage distribution across the FET stack.
Solution Approach 2:
Inductors are introduced as intermediary elements between the bias voltage sources and the FET drain/body terminals. These inductors act as mediators that selectively impede DC leakage current while allowing RF signals to pass through, thereby preventing de-biasing effects without interfering with the switch's primary RF function.
2Power
If stacked FET configuration is used to handle large RF power, then power handling capability is improved, but GIDL current increases leading to severe de-biasing effects in the middle of the stack
Solution Approach 1:
The patent modifies the bias network parameters by introducing inductors with specific impedance values that are optimized for the operating frequency range. These inductive elements create frequency-dependent impedance that blocks DC GIDL current while maintaining low insertion loss for RF signals, thereby enabling the stacked configuration to handle high RF power without excessive leakage current penalties.
3Ease of operation
If inductive bias ladders are used to reduce de-biasing effects, then DC voltage distribution uniformity is improved, but device complexity increases due to additional inductor components
Solution Approach 1:
The inductive bias ladders serve multiple functions simultaneously: they block DC leakage current, maintain uniform DC voltage distribution, and preserve RF signal integrity. This multi-functionality reduces the need for separate compensation circuits or additional control mechanisms, thereby limiting the increase in overall device complexity despite adding inductor components.
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 use of inductive bias ladders significantly reduces the de-biasing effects, leading to more uniform DC voltage distribution across the switch stack, thereby extending the lifespan of transistors and improving the overall performance of RF switches by minimizing transistor breakdown.
Implementation Method 1
a drain bias ladder comprising one or more drain inductors coupled across drain and source terminals of corresponding one or more first FETs
Data Source
AI summary
Methods and devices to reduce the gate-induced drain/body leakage current (GIDL) generated in FET switch stacks when in OFF state are disclosed. Such devices include inductors as part of bias networks coupled with drain/source terminals and/or body terminals of the transistors within the switch stack. Hybrid approaches where resistors in combination with inductors are implemented as part the bias network are also described.