Series RF Switch Topology Without Charge Pump Biasing
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Solution Overview
Problem
Conventional RF switches require a charge pump for negative voltage biasing, leading to increased area and power consumption, which complicates chip integration and increases costs while also generating harmonics due to potential switching between high and low impedance states with RF signal frequencies.
Innovation Solution
An RF switch circuit design that bypasses parasitic capacitances by conductively coupling control terminals with the switch terminals, allowing positive biasing of inner transistors without a negative substrate bias, eliminating the need for a charge pump and preventing harmonic generation by ensuring transistors remain in high impedance state across RF signal ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a charge pump is integrated to provide negative voltage biasing for substrate and gates, then voltage stability and linearity are ensured, but chip area increases and manufacturing complexity increases
Solution Approach 1:
The patent extracts and removes the charge pump component from the RF switch circuit, eliminating the need for negative voltage biasing. The circuit is redesigned to operate with positive voltage biasing only, thereby simplifying chip integration while maintaining voltage stability through alternative circuit topology using series-connected transistors with gates connected to sources.
Solution Approach 2:
The patent inverts the conventional biasing approach by using positive voltage biasing instead of negative voltage biasing. The substrate is biased with positive voltage relative to source-drain nodes, and transistor gates are connected to sources rather than requiring negative gate bias, fundamentally changing the voltage reference scheme to eliminate the charge pump.
2Reliability
If a charge pump is integrated to provide negative voltage biasing, then transistor linearity is ensured, but additional process steps are required and manufacturing cost increases
Solution Approach 1:
The charge pump is completely removed from the circuit design, eliminating the need for additional manufacturing process steps associated with integrating charge pump circuits. The RF switch achieves linearity through the series connection topology and positive biasing scheme without requiring the complex charge pump integration processes.
3Productivity
If transistors switch between high and low impedance states at RF signal frequencies, then switching function is achieved, but harmonic generation occurs
Solution Approach 1:
The patent applies preliminary action by pre-biasing the substrate with positive voltage and connecting transistor gates to their respective sources before RF signal application. This preliminary biasing configuration ensures that transistors operate in a controlled manner during switching, preventing the generation of harmonics while maintaining high-speed switching capability.
4Reliability
If conventional switch design with charge pump is used, then negative voltage biasing is achieved, but power consumption increases
Solution Approach 1:
The charge pump, which is a power-consuming component, is extracted and removed from the circuit. The RF switch circuit now operates without active voltage generation components, relying instead on passive positive voltage biasing through the series transistor configuration, thereby significantly reducing power consumption while maintaining voltage control.
Data Source
AI summary
An RF switch circuit for switching RF signals includes a first terminal and a second terminal and a series connection of a plurality of transistors between the first terminal of the RF switch circuit and the second terminal of the RF switch circuit. Furthermore, the RF switch circuit includes a control circuit configured to conductively couple, in a high impedance state of the RF switch circuit, the first terminal of the RF switch circuit to a control terminal of a first transistor in a series of the series connection of the plurality of transistors. The second terminal of the RF switch circuit is conductively coupled to a control terminal of a last transistor in the series of the series connection of the plurality of transistors.