Stacked RF Amplifier Body-Tie Layout for Voltage and Transient Control
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Solution Overview
Problem
Traditional RF amplifiers using stacked SOI devices do not incorporate body ties due to limitations such as increased parasitic capacitance, larger layout area, and design tool limitations, which degrade performance in terms of voltage capability, ON state conduction, and speed.
Innovation Solution
The use of a combination of three-terminal and four-terminal transistors in a stacked RF amplifier configuration, where at least one transistor is a four-terminal device with a body tie, improves performance by reducing floating body effects and enhancing voltage and power handling capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If body ties are added to SOI transistors in RF amplifiers, then voltage capability and power handling are improved, but parasitic capacitance increases and layout area enlarges
Solution Approach 1:
The patent segments the transistor stack into different configurations: some transistors are implemented as three-terminal devices without body ties, while others are four-terminal devices with body ties. This segmentation allows the circuit to benefit from the high voltage capability of body-tied transistors in specific positions (where high voltage stress occurs) while avoiding the parasitic capacitance penalty in other positions, thus resolving the contradiction between voltage capability and device complexity.
2Strength
If body ties are added to SOI transistors in RF amplifiers, then breakdown voltage increases, but layout area increases
Solution Approach 1:
The patent applies local quality by providing body ties only to specific transistors within the stacked configuration where high breakdown voltage is critically needed, rather than uniformly applying body ties to all transistors. This localized approach ensures that the layout area increase is minimized while still achieving the necessary breakdown voltage enhancement in critical regions of the amplifier.
3Reliability
If body ties are added to SOI transistors, then hot carrier injection performance improves, but ON state conduction degrades
Solution Approach 1:
The patent segments the transistor stack to apply body ties selectively to transistors where hot carrier injection resistance is most critical, while leaving other transistors as three-terminal devices to maintain optimal ON state conduction. This segmentation allows the circuit to achieve improved hot carrier injection performance in specific locations without degrading the overall ON state conduction characteristics of the amplifier.
Data Source
AI summary
A transistor stack can include a combination of floating and body tied devices. Improved performance of the RF amplifier can be obtained by using a single body tied device as the input transistor of the stack, or as the output transistor of the stack, while other transistors of the stack are floating transistors. Transient response of the RF amplifier can be improved by using all body tied devices in the stack.