AD620 IC

Hi All,

I have two ICs name AD620 548181 and AD620 33756. Both the ICs have same features but the problem is that when i was interchanging both each other only AD62033756 is work properly. The problem is not only with single piece of AD62054818, I have order 10 ICs piece of AD62054818 and all are not work in place of AD62033756 .