Series RF Switch Circuit Without Charge Pump Biasing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional RF switches require a charge pump for negative voltage biasing, leading to increased area and power consumption, and potential harmonic generation due to transistor switching between high and low impedance states with RF signal frequency.
Innovation Solution
An RF switch circuit with a series connection of transistors and a control circuit that bypasses parasitic capacitances by conductively coupling control terminals to terminals, allowing positive biasing of inner transistors without a negative substrate bias, eliminating the need for a charge pump and preventing harmonic generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a charge pump is integrated to provide negative voltage biasing for transistor gates and substrate, then voltage stability and linearity are ensured, but chip area increases and manufacturing complexity increases
Solution Approach 1:
The patent extracts and eliminates the charge pump component from the RF switch circuit. By using a series connection of transistors where the substrate is connected to the drain of each transistor, negative substrate biasing is achieved inherently without requiring an external charge pump, thus reducing chip area and manufacturing complexity while maintaining voltage stability
Solution Approach 2:
The transistor series connection structure provides self-biasing functionality. Each transistor in the series connection automatically establishes the required negative substrate bias through its drain connection to the substrate, eliminating the need for separate biasing circuitry and making the system self-sufficient
2Productivity
If transistors are switched between high and low impedance states at RF signal frequency, then RF signal switching is achieved, but harmonic generation occurs
Solution Approach 1:
The patent segments the RF signal path into multiple transistor stages connected in series. Each transistor operates at a different impedance level, and the series connection distributes the voltage swings across multiple devices, reducing the impedance modulation depth at any single transistor and thereby minimizing harmonic generation while maintaining fast switching capability
3Loss of energy
If multiple transistors are connected in series for RF switching, then insertion loss is reduced and power stability is improved, but control complexity increases
Solution Approach 1:
The patent merges the control functions for multiple transistors into a unified control scheme. By connecting the substrate to the drain of each transistor in the series chain and using a common substrate bias, the control of multiple transistors is simplified and coordinated, reducing control complexity while maintaining the low insertion loss and high power stability benefits of the series configuration
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.