Analog switch ADG1421 to single opamp singnal conditioning.

[davezap]

Hi.. long time lurker here.

My circuit needs to do ADC on an inductive load for one cycle I wish to sample the top side of the inductor and on the other cycle the bottom.

I could just use two opamps but thought it would be good to be able to disconnect the inductor completely such that the noise in this part of the circuit could be sampled and used to cancel later on.

Was looking at using this Analog Devices part. With both drains connected to the input of the opamp.

https://www.analog.com/static/imported-files/data_sheets/ADG1421_1422_1423.pdf

Now the question.

In the general description it states "In the off condition, signal levels up to the supplies are blocked." - So I am to take that to mean if the signal goes either side of Vss or Gnd it would pass through?

I guess the internals are like a mosfet with a protection diode? Does that sound correct?

Thanks.

 

[erikl]

I guess the internals are like a mosfet with a protection diode? Does that sound correct?

Yes, 2 protection diodes, one to GND & one to VDD, with a common protection series resistor.

In the general description it states "In the off condition, signal levels up to the supplies are blocked." - So I am to take that to mean if the signal goes either side of Vss or Gnd it would pass through?

No, such signal would be limited inside the ADG1421 to one diode forward voltage drop below GND or above VDD, and so would be blocked as well.