INA148: Differential input without supply

Hi Thomas,

Question 1:

Is an input voltage of 15V (between Vin+ an Vin-) allowed if there is no supply voltage? The supply voltage and Ref is on ground. 

This is likely going to be ok, since the input impedance of the part is 2 Mohm in differential mode and input voltage is below the absolute max. ratings of the part. In addition, there is a current path to ground for the op amp. 

Since you are doing dielectric withstand  or insulation resistance test, the breakdown leakage current test for 60 seconds is standard test for certain industries, e.g. aerospace. 

Question 2:

If the input voltage is 15V and there is no supply voltage connected (or on ground) what are the maximum values for the output voltage?

if 15V is applied between Vin+ and Vin- without supply voltage and ground connection, I would say that you should see 0 voltage at the output of  the amplifier. INA148 is a bipolar op amp  device. Since there are no bias voltages present at the 1st to 3rd stages of op amp circuit, there should not be a current path between input to output.  

Best,

Raymond