RF Transistor Stack Capacitor Network for Off-State Voltage Balancing
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Solution Overview
Problem
Conventional RF switches with stacks of field effect transistors (FETs) face issues with non-uniform RF voltage distribution, leading to low power handling capability and high off-state leakage currents, resulting in undesirable signal losses.
Innovation Solution
Incorporating a capacitor network across multiple transistors in the stack to balance RF voltages, reducing off-state leakage currents and enhancing the stack's ability to withstand high power signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional FET stacks are used in RF switches, then the switch can provide signal path routing, but non-uniform RF voltage distribution results in low power handling capability
Solution Approach 1:
Capacitors are introduced as intermediary elements coupled between adjacent FETs in the stack. These capacitors act as mediators to equalize the RF voltage distribution across the FETs by providing an AC coupling path that balances the voltage stress, thereby enabling the stack to handle higher power signals uniformly across all devices.
2Reliability
If conventional FET stacks are used in RF switches, then the switch can provide signal path routing, but high off-state leakage currents result in signal losses
Solution Approach 1:
The capacitors coupled between FETs in the stack serve as intermediary elements that balance the RF voltage distribution during off-state operation. By equalizing the voltage stress across adjacent FETs, the capacitors prevent excessive voltage on individual devices that would otherwise cause high leakage currents, thereby reducing signal losses.
3Power
If capacitor networks are added to balance RF voltages, then power handling capability improves, but device complexity increases
Solution Approach 1:
The capacitor network is segmented and distributed across multiple FETs in the stack rather than using a single complex capacitor. Each capacitor is coupled between adjacent FETs, dividing the voltage balancing function into simpler, modular segments that are easier to implement and integrate into the existing FET stack structure.
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 capacitor network balances RF voltages across the transistors, reducing leakage currents and signal losses, thereby improving the power handling capability of the RF switch.
Implementation Method 1
a first capacitor of the capacitor network coupled across a first pair of adjacent transistors of the first group, and a second capacitor of the capacitor network coupled across a second pair of adjacent transistors of the first group
Implementation Method 2
Conventional techniques for balancing the RF voltage distribution may result in undesirably high levels of leakage currents when the stack is in the off state
Data Source
AI summary
A switch circuit includes a transistor stack coupled between first and second ports. The transistor stack includes a group of multiple, adjacent, series-coupled transistors, and at least one additional transistor coupled in series with the group between the first and second ports to provide a first variably-conductive path between the first and second ports. The switch circuit also includes a balancing capacitor with a first terminal coupled to an input of the group of multiple, adjacent, series-coupled transistors, and a second terminal coupled to an output of the group of multiple, adjacent, series-coupled transistors.