[SOLVED] No gain resistor on op-amp: what I do?

[Lucast85]

Hello people,
I use a differential OPAMP that is AD8220. The gain I need is 1 so I not use an external Rg resistor and i must leave Rg pins disconnected.

In PCB design, this can lead to have some high frequencies disturbances on this pin? It's better to put some capacitors between Rg pins and gnd ? If yes, what value?

Thank you!!

 

[Tunelabguy]

No, you should leave the gain resistor pins disconnected. If you look at the datasheet for the chip you will see that these pins already have resistors connected internally. They are not high-impedance inputs. These pins carry the signal on them, so putting capacitors would short-circuit the feedback operation and make the opamp unstable.

 

[Lucast85]

Thank you for your quickly and clear explanation!!
:wink: