opa211 output impedance when shutdown

Hi John,

The direct OPA211 output impedance in shutdown wasn't characterized, but an effort was made to measure the various node currents in shutdown. They should provide some idea of the current in that mode.

The data shown below indicates that the output current is a fraction of a nanoamp, which would indicate that the static impedance is very high, possibly Megohms, undr dc conditions. The output transistors are biased off in this condition and we would expect the impedance to be very high.

If the output is back-driven by a voltage source and the current measured the dynamic impedance could be determined. Since things should stay off, the impedance should remain high as long as the swing level doesn't begin to turn on the ESD cells. I would expect the dynamic impedance under ac conditions to become lower because circuit parasitics come into play. It would be best test the OPA211 in your circuit, place it in disable mode, and see if the performance meets the system requirements. 

Regards, Thomas

PA - Linear Applications Engineering

Thanks for your help.