Constant vgs analog switch and method used on the constant vgs analog switch

Abstract

Apparatus and methods for a switch circuit to provide a substantially constant gate-to source voltage to a passgate are provided. In an example, a switch circuit includes a summing circuit having an output configured to couple to the gate of a passgate, the summing circuit can be configured to maintain a substantially constant voltage between the gate and the source of the pass gate.

Description

technical field [0001] The present application relates to apparatus and methods for switching circuits, and more particularly, to switching circuits including summing nodes configured to reduce distortion of switching signals. Background technique [0002] Metal Oxide Semiconductor Field Effect Transistor (MOSFET) devices can be used as switches for connecting electrical signals. Typically, MOSFET devices have little or no offset voltage that is present in solid-state switches such as bipolars. Typically, the MOSFET switch on-resistance (R on ) is very low while the off resistance (R off )very high. In modern installations, R on can be ohms or smaller, and R off Can be many megohms. In a MOSFET switch, R on may be a function of the gate-source voltage Vgs of the device. because R on is a function of Vgs, so if Vgs is constant or other things are equal, then R on Can also be constant. When these switching devices are used for audio signals, if R on As the voltage ...

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Problems solved by technology

However, since the power supply voltage used to generate the logic signal voltage can vary with the load, this causes the logic signal voltage value to vary accordingly

This change in Vgs can change R on , and thus limits the useful dynamic range of the '874 patent to

Also, in applications with large negative signal swings, the reliability of the MOSFET will be compromised due to the degradation of the gate oxide of the MOSFET

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