INA117: Can its pin 8 (Comp) be floated? what happens if it is floaing?

Hi John,

The older INA117 has the requirement that pin 8 be connected to ground directly, or through a capacitor (100 nF) through a ground return. The datasheet says "Internal circuitry connected to the compensation pin 8 cancels the parasitic distributed capacitance between the feedback resistor, R2, and the IC substrate. For specified dynamic performance, pin 8 should be grounded or connected through a 0.1µF capacitor to an AC ground such as V+."

If the pin floats there may be some degradation of dynamic AC performances. What they may amount to is not known, but it will likely be small. Since there really isn't any other option beyond revising the PC board the only practical thing to do is try the INA117 in the INA149 application and see if satisfactory circuit performance is achieved. There aren't any reliability implications if the INA117 compensation pin is floated.

Regards, Thomas

Precision Amplifiers Applications Engineering