hi.. we r working on a project where we use a micromachined tri-axial accelerometer to capture the knee joint motion signals. we are using TL084 to amplify and filter the signals.
our accelerometer works on a power supply of max 3 V whereas the IC will work on min 7 V. we are confused as to which power supplies to use as our device has to be as small as possible and portable. please help!!!!

 

You did not mention the circuit's requirements for the opamp (noise figure, offset, etc.)

You can use the TL084 if you use separate power supplies for the opamps and the accelerometer.

If you want an opamp that can run from a lower power supply voltage, you can use something like the NJU7054 (New Japan Radio Company), which can operate with only a 1 volt power supply or the TLC274 (TI) which can operate from a single 3 volt power supply over the 0°C to 70°C temperature range.