Analog switches and methods for controlling analog switches

摘要

An analog switch may be maintained reliably in an off state. The switch comprises: a P-type first transistor having a source, a drain and a gate, a N-type second transistor having a source, a drain and a gate, and a switch control circuit to drive the gates of the first and second transistors. The drain of the first transistor and the source of the second transistor are connected at a first node, and the source of the first transistor and the drain of the second transistor are connected at a second node. When the voltage at the first or second nodes falls outside of a supply voltage range of the switch control circuit, the switch control circuit is operable, in response to a signal to make the switch high impedance, by adjusting the gate voltages of the first transistor and the second transistor.

主权项

1. An analog switch that adjusts voltages on its switching transistors to meet a desired switching state, comprising:
a P-type first transistor having a source, a drain and a gate; an N-type second transistor having a source, a drain and a gate where the source of the second transistor is directly coupled to the drain of the first transistor at a first node and the drain of the second transistor is directly coupled to the source of the first transistor at a second node; a switch control circuit configured to:
drive the gates of the first and second transistors, wherein the driving permits or inhibits signal transmission through the analog switch depending on a control signal,wherein if the control signal indicates that signal transmission is permitted and a voltage of an input signal at the first or second node falls outside of a supply rail voltage range of the switch control circuit, the driving applies a voltage corresponding to the voltage of the input signal, thereby permitting the input signal to pass between the first and second nodes, andwherein when the voltage at the first or second node falls outside of the supply rail voltage range of the switch control circuit and signal transmission is inhibited, the switch control circuit drives the gate of the first transistor with a voltage corresponding to the most positive voltage of the voltage at the first node and the voltage at the second node and drives the gate of the second transistor with a voltage corresponding to the most negative voltage of the voltage at the first node and the voltage at the second node.