Hello my friends,
I have to use an AD8599 and I tried to measure the CMRR with Vcc=+/-5V with -2V<Vcm<2V (as noted in the datasheet). The result is about 110bB (vs 120dB Min). I tried using conditions Vcc=+/-15V with -12.5V<Vcm<12.5V and it's the same. I carry out these measurements with DC conditions.
Could you help me if you know conditions to reach the value given in the datasheet?
I tried 2 bias methods:
In accordance with MIL-STD: Vcc+=+7V; Vcc-=-3V; Vin=+2V and Vcc+=+3V; Vcc-=-7V; Vin=-2V
with a direct method (instrumentation amplifier between In+ and In-): Vcc+=5V; Vcc-=-5V; Vin=-2V then Vin=+2V
The Delta of the Vio is about 10µV with -2V<Vcm<2V.
Then, I downloaded the Pscipe model on the AD website... I've got the same results!
I have another comment, I think there is a mistake on the datasheet Rev. C (page 3): the condition of the Open Loop Gain with Vsy=+/-5V specifies -11V<Vo<11V... Wahoo... Beyond the rail!!!
Thank you for your answers.
Alex.
