RF FET Switch Biasing Without Negative Voltage Spurs
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Solution Overview
Problem
Radio frequency (RF) switching devices that use field-effect transistors (FETs) require a negative bias voltage to operate effectively, which is typically generated by an oscillator that can introduce spurious emissions due to injected spurs.
Innovation Solution
A biasing scheme that uses only non-negative DC voltages to control FETs, eliminating the need for an oscillator and charge pump, thereby reducing spurious emissions and simplifying the circuitry by requiring only two bias voltages and control lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a negative voltage generator including an oscillator and charge pump is used to generate negative bias voltage, then the FETs can be biased in an off state, but spurious emissions are caused due to oscillator injected spurs
Solution Approach 1:
The patent extracts and removes the oscillator component from the negative voltage generator. By eliminating the oscillator, the source of spurious emissions (injected spurs) is removed while the essential function of generating negative bias voltage for FET off-state operation is preserved through alternative means that do not require oscillation.
Solution Approach 2:
The patent converts the harmful effect of oscillator spurs by replacing the oscillator-based voltage generation with a non-oscillator-based approach. The harmful spurious emissions are transformed into a beneficial situation where no spurs are generated, achieving clean RF operation while maintaining FET control capability.
2Reliability
If a negative voltage generator with oscillator and charge pump is used, then negative bias voltage can be generated, but the circuit complexity increases
Solution Approach 1:
The patent removes the oscillator component from the voltage generator circuit, thereby reducing circuit complexity. The essential function of generating negative bias voltage is maintained through a simplified architecture that eliminates the need for oscillation and charge pumping, resulting in a less complex overall circuit design.
Solution Approach 2:
The patent employs a multi-functional approach where a single simplified voltage generator structure performs the negative bias voltage generation without requiring separate oscillator and charge pump circuits. This universal design achieves the same functional outcome with reduced component count and lower circuit complexity.
Data Source
AI summary
Embodiments provide a switching device including one or more field-effect transistors (FETs) and bias circuitry. The one or more FETs may transition between an off state and an on state to facilitate switching of a transmission signal. The one or more FETs may include a drain terminal, a source terminal, a gate terminal, and a body. The biasing circuitry may bias the drain terminal and the source terminal to a first DC voltage in the on state and a second DC voltage in the off state. The first and second DC voltages may be non-negative. The biasing circuitry may be further configured to bias the gate terminal to the first DC voltage in the off state and the second DC voltage in the on state.