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switching transient on ADG888

Question asked by shoots on Jan 17, 2017
Latest reply on Jan 17, 2017 by harryh

I am trying to use an ADG888 switch as a clamp across the inputs to an amplifier. The signal input is from a pair of electrodes applied to the body adjacent to a target muscle. The clamp is intended to prevent the amplifier saturating when a magnetic field is triggered alongside the nerve activating the muscle- some 300mm from the muscle. The clamp is activated a few milliseconds before the magnetic field is triggered and then released a few milliseconds after the field collapses.

 

The problem I am having is a spike appearing on the signal co-incident with the ADG888 switching on and off. This is without any muscle activation signal so no input signal. The ADG888 was controlled via a NAND gate, However the issue with the spike also appears when using a simple battery to control the IC. I am suspecting that it is originating within the ADG888 and is caused by the charge injection from the control signal.

 

In the attached cro shot the blue trace is the switching signal and yellow the  spike observed on one of the switched pins

Is there any way to prevent this or can you suggest an alternate approach to clamping the signal artefact?

Thankyou, Peter.

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