thnx for all ... i was using DC power supply ...but now im using 9v batteries and isolate myself and my work from electricity.... but i got a sequre wave on the output of AD620 ..... my friend told me that the transistors reched saturation region so change the input voltage to 3v ....but i see most of researchs used 12v as input ....any one have used AD260 before can help me ?? i will make a new topic for that ...thnx again