Input impedance of AD8220 with ADG1209

In my previous design, AD8220 was chosen because of the requirement of the extremely high input impedance. However, I need to modify the circuit design by adding a demultiplexer to perform a 1 to 4 switch function and ADG1209 seems suitable for my design.

However, if I add an ADG1209 after AD8220, how will it affect the input impedance of the system?

I need to maintain a high input impedance.

I attach my AD8220 circuit design in this post. ADG1209 will be added after R11 and R12.

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  • Hi cklooi,

    Thank you for your interest in ADI parts. Placing a multiplexer in your signal chain should not cause any problem on the input impedance. However, most MUX errors are due to Ron and leakage current. Ron tends to form a resistor divider network with the MUX load (which is mostly the input impedance of the amplifier) while the leakage current and the MUX load creates an additional offset voltage error. Also, take note of the amplifier's settling time as this will be a factor on how fast your switching should be. You can read more on multiplexer on this tutorial or you can visit the Switches and Multiplexers Community.

    Best regards,

    Neil

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  • Hi cklooi,

    Thank you for your interest in ADI parts. Placing a multiplexer in your signal chain should not cause any problem on the input impedance. However, most MUX errors are due to Ron and leakage current. Ron tends to form a resistor divider network with the MUX load (which is mostly the input impedance of the amplifier) while the leakage current and the MUX load creates an additional offset voltage error. Also, take note of the amplifier's settling time as this will be a factor on how fast your switching should be. You can read more on multiplexer on this tutorial or you can visit the Switches and Multiplexers Community.

    Best regards,

    Neil

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