MOSFET High-Frequency Switch Biasing to Suppress Signal Distortion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High frequency switches used in wireless communications, such as GSM terminals, suffer from signal distortion due to parasitic diodes in MOSFETs, which are not effectively addressed by existing technologies.
Innovation Solution
A capacitor is connected between the body terminal and the drain terminal of MOSFETs connected to the common port, feeding-forward the power transmission signal to prevent parasitic diode conduction and thereby reducing signal distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high frequency switch uses MOSFETs formed on a silicon substrate to handle large power transmission signals, then the power transmission capability is improved, but parasitic diodes become conductive causing signal distortion
Solution Approach 1:
The patent applies preliminary anti-action by connecting a capacitor between the body terminal and drain terminal of the MOSFET to preemptively counteract the parasitic diode conduction problem. The capacitor feeds forward the transmission signal to the body terminal, establishing reverse bias on the parasitic diode before the harmful conduction can occur, thereby preventing signal distortion while maintaining high power transmission capability
Solution Approach 2:
The patent uses a capacitor as an intermediary element to transfer the transmission signal from the drain terminal to the body terminal. This intermediary component enables the feed-forward mechanism that maintains reverse bias on the parasitic diode, solving the contradiction between power handling and signal integrity without requiring fundamental changes to the MOSFET structure
2Strength
If voltages are evenly divided and applied to multiple series-connected FETs, then the withstand voltage characteristics are improved, but parasitic diode conduction still occurs causing distortion
Solution Approach 1:
The patent applies local quality by targeting the specific MOSFET connected to the common port with the capacitor connection. Instead of modifying all FETs uniformly, the invention locally addresses the problematic device where the parasitic diode conduction occurs, feeding forward the signal to its body terminal to maintain reverse bias while leaving other devices unchanged
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 effectively suppresses distortion characteristics in high frequency switches by maintaining reverse bias on parasitic diodes, improving signal integrity and reducing chip size increases.
Implementation Method 1
a capacitor connected between a body terminal of a MOSFET connected to a common port, among MOSFETs configuring each switching unit, and a terminal (a drain terminal) connected to the common port
Data Source
AI summary
There is provided a high frequency switch capable of suppressing deterioration in distortion characteristics. The high frequency switch includes: a common port outputting a transmission signal to an antenna; a plurality of transmission ports each having the transmission signal input thereto; and a plurality of switching units each connected between the plurality of transmission ports and the common port to conduct or block the transmission signal from each of the transmission ports to the common port, wherein each of the switching units has one or more metal oxide semiconductor field effect transistors (MOSFETs) formed on a silicon substrate, and a capacitor connected between a body terminal of a MOSFET connected to the common port among the MOSFETs and a terminal of the MOSFET connected to the common port.