Off-amps, What The Heck Are Off-amps? Op Amps With No Power Applied, Of Course

摘要

Q. What kind of performance (pick a parameter, it could be input impedance or any other op amp specification) can I expect from your amplifier... when the power is off?rnA. This may seem like a strange question, but as the title says, "Strange stories from the call logs..." A few times a year we receive questions like this. The specifics vary slightly from customer to customer, but ultimately they want to know how the off-amp will behave in their circuit. A recent customer email asked if the high input impedance of a FET amplifier would be maintained with the power off and a dc voltage at the amplifier input. The short answer was no, but they could maintain a high input impedance over a limited input voltage range by adding a few well placed external diodes.