RF Switch FET Stack Voltage Equalization via Compensation Circuits
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
RF switches using FET stacks face challenges in maintaining high power handling capability while ensuring fast switching speed, as unequal source-drain voltages across FETs can lead to breakdown, requiring a solution to equalize voltages across each FET in the stack.
Innovation Solution
The implementation of compensation circuits that electrically couple the body of one FET to the gate of another within the FET stack, using impedance-providing components such as capacitors or RC series circuits, to compensate for parasitic leakage currents and equalize source-drain voltages across FETs when the switch is open.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If series-coupled FET stacks are used to increase power handling capability, then voltage distribution across FETs becomes unequal, but this leads to breakdown risk and reduced reliability
Solution Approach 1:
A compensation circuit is introduced as an intermediary element between FETs in the series stack. This circuit includes a capacitor connected between the body of one FET and the gate of another FET, acting as a mediator to redistribute voltage and compensate for unequal voltage distribution across the FETs, thereby preventing breakdown while maintaining high power handling capability
Solution Approach 2:
The invention changes the electrical parameters (voltage distribution) across the FETs by introducing capacitive coupling. The capacitor modifies the voltage parameters dynamically during switching operations, equalizing the voltage stress across each FET in the series stack and enabling reliable high-power operation
2Power
If FET stacks are used for high power handling, then switching speed may be compromised, but fast switching is required for RF applications
Solution Approach 1:
The compensation circuit with capacitive coupling acts as an intermediary that enables both high power handling and fast switching. The capacitor provides a charge storage mechanism that facilitates rapid voltage transitions during switching while maintaining proper voltage distribution, thus preserving switching speed despite the use of series-coupled FET stacks
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 approach enhances the power handling capability of RF switches while maintaining high switching speed by ensuring uniform voltage distribution across FETs, preventing excessive voltage that could lead to FET failure.
Implementation Method 1
the first compensation circuit includes a capacitor configured to compensate for the effects of the body-source parasitic leakage currents
Implementation Method 2
the first compensation circuit includes a resistor-capacitor (RC) series circuit whose impedance is configured to compensate for the effects of the body-source parasitic leakage currents
Data Source
AI summary
Embodiments described herein include radio frequency (RF) switches that may provide increased power handling capability. In general, the embodiments described herein can provide this increased power handling by equalizing the voltages across transistors when the RF switch is open. Specifically, the embodiments described herein can be implemented to equalize the source-drain voltages across each field effect transistor (FET) in a FET stack that occurs when the RF switch is open and not conducting current. This equalization can be provided by using one or more compensation circuits to couple one or more gates and transistor bodies in the FET stack in a way that at least partially compensates for the effects of parasitic leakage currents in the FET stack.