ADA4898-1YRDZ - Output is high, when input is floating

Hi.

We are using PN# ADA4898-1YRDZ in out board as a unit gain amplifier.

Refer the image for the schematic

when non inverting input is floating (pin 3) we are observing 7V at output side (pin 6).

Can you please help me;

1. why offset observed at output (pin 6).

2. can input pin left floating. will it harm the chip. (note: chip temp is normal when input is floating)

During testing measured

Non-inverting input = 10mV (floating)

Output = 7V

Project Details: Test board

Annual QTY: 1000 PCS

Circuit:

Thanks and Regards,

Senthil

  • Hi Senthil,

    The output when one or more inputs are floating is not considered offset. When the input pin is left floating, it can be at a random potential and may cause the output to swing to "0" or "1" logic. To get the offset voltage, both pins could be grounded. Here is a reference to know more how to deal with unused inputs.

    All the best!