HI Folks.First post here so be kind.
Several years back when trying to fits a circuit into a very small space one would stack the chips. Very common re adding memory to existing populated boards. You just solder the new ones on but lift the address pins and wire them seperately.
I have a need to do this with a stack of AD620's. I have 10 that I will be doing this for.
What I would like to know is can I use one gain resistor to control the lot.. Or will I need a separate resistor for each chip. It will be for a EMG circuit so the gain will be the same across all channels.
e.g. for 2 chips (A, B)
Pins A1 to B1Pins A4 to B4Pins A5 to B5Pins A7 to B7
Pins A8 to B8
Then put the master gain resistor on A1 and A8.. Or will I need to have a separate resistor for each amp.
All other pins separated and raised for other leads to connect.
I'm afraid that's not possible. If you have space constraints, maybe I can suggest the dual In-Amps AD8222, AD8224, or AD8426, that come in LFCSP packages (much smaller than AD620. Alternatively, for multiple-lead ECG, you could consider ADAS1000.