RF Switch Body-Bias Circuit for High-Power Low-Loss Operation
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Solution Overview
Problem
RF switches face challenges in withstanding high RF power due to increased series resistance from stacking MOSFETs, leading to increased parasitic capacitance and chip size, which limits the improvement of voltage handling capabilities.
Innovation Solution
The implementation of a radio frequency (RF) switch with a bias switch connected between the control and body terminals of the switch transistor, allowing a negative voltage to be applied when the switch is off, and using a synchronous self-body bias method to synchronize the voltage of the body and gate terminals, reducing series resistance and parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If two or more MOSFETs are stacked in series to withstand high voltage, then the withstanding voltage is improved, but the series resistance increases leading to increased RF insertion loss
Solution Approach 1:
The patent applies a negative voltage to the body terminal of the MOSFET, changing the electrical parameter of the body terminal from ground potential to negative potential. This parameter change reduces the parasitic capacitance between the body and drain terminals, thereby reducing RF insertion loss while maintaining the high voltage withstanding capability of the stacked MOSFET configuration
2Loss of energy
If the size of MOSFET is increased to reduce series resistance, then the RF insertion loss is reduced, but the parasitic capacitance increases and chip size increases
Solution Approach 1:
Instead of increasing the physical size of the MOSFET to reduce series resistance, the patent changes the electrical parameter by applying a negative voltage to the body terminal. This reduces parasitic capacitance effects, allowing smaller MOSFET sizes to achieve the same RF performance, thereby reducing chip size while maintaining low RF insertion loss
3Loss of energy
If appropriate voltage is applied to gate and body terminals to reduce parasitic capacitance, then parasitic capacitance and chip size are reduced, but the improvement is limited as RF power increases
Solution Approach 1:
The patent dynamically adjusts the body terminal voltage based on the operating state of the switch. When the switch is off, a negative voltage is applied to the body terminal to minimize parasitic capacitance and RF leakage. This dynamic voltage adjustment maintains optimal performance across varying RF power levels, overcoming the limitations of static biasing approaches
Data Source
AI summary
A radio frequency (RF) switch is provided. The RF switch includes: a switch transistor that includes a first terminal to which a radio frequency (RF) signal is input, a second terminal to which the RF signal is output, a control terminal to which a first level voltage and a second level voltage are applied in response to a control signal, and a body terminal to which a bias voltage is applied; and a bias switch connected between the control terminal and the body terminal of the switch transistor and configured to turn on when the switch transistor is turned off to apply the second level voltage to the body terminal.