RF FET Switch Stack Gate Bypass for High-Impedance Steady States
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Solution Overview
Problem
Existing RF switch FET stacks with gate resistor networks face challenges in reducing switching time due to the high impedance status during steady states and transition states, which affects the efficiency of RF signal switching.
Innovation Solution
A dynamic gate control block is introduced, comprising a series combination of nMOS and pMOS transistors that bypass the common gate resistors during transition states while maintaining high impedance during steady states, allowing for efficient RF signal switching by controlling the gate voltages of the transistors to establish low impedance status during transitions and high impedance status during steady states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gate resistors are used in the FET switch stack, then the high impedance status is maintained during steady states, but the switching time increases due to the impedance limiting the charging/discharging speed of gate capacitance
Solution Approach 1:
The patent applies the dynamics principle by making the gate resistor impedance dynamic rather than static. A bypass switch (controlled by control signals) is connected in parallel with the gate resistors, allowing the impedance to switch between high (during steady state) and low (during transition). This dynamic impedance change enables the circuit to maintain high impedance for stability during steady states while providing low impedance paths during transitions to rapidly charge/discharge gate capacitance, thereby reducing switching time without compromising steady-state performance.
2Ease of operation
If gate resistors are used to control FET gates, then the FET switches can be properly biased, but the resistors create stress on the transistors during switching transitions
Solution Approach 1:
The patent applies the intermediary principle by introducing a bypass switch as a mediator between the control signal and the FET gate. During transition periods, the bypass switch activates and provides an alternative low-impedance path that shields the FET from the full stress of rapid voltage changes through the gate resistor. The bypass switch acts as an intermediary that handles the high-current switching transient, while the gate resistor continues to provide gentle bias control, thereby reducing stress on the FET transistor during switching transitions.
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 reduces switching time and improves the efficiency of RF signal switching by effectively bypassing the gate resistors during transitions, thereby reducing stress on the transistors and enhancing the reliability of the RF switch FET stacks.
Implementation Method 1
bypass the one or more common gate resistors during at least a transition portion of the transition state... establishing a low impedance status during transitions
Implementation Method 2
the nMOS transistor and the pMOS transistor being both in an ON state during said transition portion... one of the nMOS transistor and the pMOS transistor being in an OFF state
Data Source
AI summary
A common gate resistor bypass arrangement for a stacked arrangement of FET switches, the arrangement including a series combination of an nMOS transistor and a pMOS transistor connected across a common gate resistor. During at least a transition portion of the transition state of the stacked arrangement of FET switches, the nMOS transistor and the pMOS transistor are both in an ON state and bypass the common gate resistor. On the other hand, during at least a steady state portion of the ON steady state and the OFF steady state of the stacked arrangement of FET switches, one of the nMOS transistor and the pMOS transistor is in an OFF state and the other of the nMOS transistor and the pMOS transistor is in an ON state, thus not bypassing the common gate resistor.