Part Number:INA217
Hi everyone,
I have no experience with IA before. I wanna make a precise subtractor and amplifier for a signal conditioning circuit to the ADC of DSP. My schematic is attached below. The signal VOSENSE is from -10.5V to 0V. My problem is that when the offset voltage (point A) is -10.3V (because the power supply is not exact -15V), the voltage of point B is only -7.22V. I checked the input impedance of pin 5 of INA217 (R14 was removed), it was 1.78 Mohm.
If I change R14 value from 10k to 47 Ohm, IA gets hot (44 degrees), the voltage at point B is slightly reduced to 10.2V.
I do not understand why the input signal going through R14 is degraded if the input impedance of IA is very high. Anything about this IA which I misunderstand here.
Thank for your help
