AD8513 is a JFET input operational amplifier with a pA range of bias current. Since it has a very low input bias current, its input impedance range will be in GΩ to TΩ range. If you look into other precision JFET operational amplifier product like ADA4610 and ADA4000, their input impedance is in TΩ range too.

If you want to solve it mathematically, you can also try to use the following formula. Common mode input resistance is the ratio of the change in input common mode voltage to the change in input bias current. For the differential input resistance, it is the ratio of the change in input differential voltage to the change in input offset current.

Hi,

AD8513 is a JFET input operational amplifier with a pA range of bias current. Since it has a very low input bias current, its input impedance range will be in GΩ to TΩ range. If you look into other precision JFET operational amplifier product like ADA4610 and ADA4000, their input impedance is in TΩ range too.

If you want to solve it mathematically, you can also try to use the following formula. Common mode input resistance is the ratio of the change in input common mode voltage to the change in input bias current. For the differential input resistance, it is the ratio of the change in input differential voltage to the change in input offset current.

I hope this helps!

Regards,

Jay