RF Switch Stack Charge Control for OFF-State Voltage Balance
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Solution Overview
Problem
RF switch stacks experience undesired leakage currents during the OFF state, leading to voltage distribution imbalances and reduced power handling capabilities due to body leakage current, which complicates DC voltage distribution and increases design costs.
Innovation Solution
Incorporating charge control elements in the drain-source and body resistive ladders of FET switch stacks, which provide tapping points for local charge support and redistribute DC voltages to maintain desired voltage levels, thereby reducing voltage drops and enhancing power handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If charge control elements are added to the resistive ladders, then voltage distribution balance is improved, but device complexity increases
Solution Approach 1:
Charge control elements are introduced as intermediary components between the resistive ladders and the transistor terminals. These elements actively mediate the voltage distribution by injecting or removing charge to compensate for leakage currents, thereby maintaining voltage balance without requiring fundamental changes to the switch stack architecture.
Solution Approach 2:
The charge control elements are configured to automatically detect and compensate for voltage imbalances caused by leakage currents. By monitoring the actual voltage distribution and dynamically adjusting charge levels, the system achieves self-regulation of voltage balance without external intervention, offsetting the added complexity through autonomous operation.
2Ease of manufacture
If resistive ladders are used for biasing, then ease of manufacture is improved, but power handling capability deteriorates due to voltage drops from leakage currents
Solution Approach 1:
The invention dynamically changes the electrical parameters (voltage levels) at critical points in the resistive ladder by introducing charge control elements. These elements adjust the effective voltage distribution in real-time to compensate for leakage-induced drops, thereby maintaining adequate voltage levels for power handling while preserving the simplicity of resistive ladder biasing.
3Power
If the switch stack is designed to block large RF voltages, then power handling is improved, but leakage currents increase causing voltage distribution imbalances
Solution Approach 1:
The invention converts the harmful effect of leakage currents into a controllable parameter. By introducing charge control elements that detect and compensate for leakage-induced voltage drops, the harmful leakage currents are transformed into a manageable condition where the charge control elements use the leakage information to actively maintain voltage balance, thereby preserving power handling capability.
Data Source
AI summary
Methods and devices to address the undesired DC voltage distribution across switch stacks in OFF state are disclosed. The disclosed devices include charge control elements that sample the RF signal to generate superimposed voltages at specific points of the switch stack biasing circuit. The provided voltages help reducing the drooping voltages on drain/source/body terminals of the transistors within the stack by supplying the current drawn by drain/source terminals of the stacked transistors and/or by sinking the body leakage current exiting the body terminals of such transistors. Methods and techniques teaching how to provide proper tapping points in the biasing circuit to sample the RF signal are also disclosed.