Problems with AD8065

[VS123]

Hi!

I've been testing a few op-amps I bought recently. AD8065 is giving me a lot of issues. I wired up a simple buffer, but got mostly noise as output. I also wired it up to have a gain of 2, but got even more noise.

Both times, I gave the circuit an input of 1 V, 300 Hz sinusoidal wave form.

I noticed that the frequency and amplitude of output became ridiculously high some times. I wasn't even able to reproduce the same results. The only thing I could tell was that there was a lot of noise, and I can't figure out why.

Any ideas??

Thanks in advance!

 

[keith1200rs]

You need to show your exact circuit. I have used the AD8065/66 in the past with no problems. It can be a bit peaky at low gains and doesn't like capacitive loads.

You need to define "noise". To me it is random, thermal or flicker noise but more likely in you case is an oscillation which would probably be at 100MHz or more. Have you checked for spurious oscillations?

Keith

 

[VS123]

Yeah, they are oscillations of about 300MHz. Why does that happen?? How can I solve the problem??

 

[keith1200rs]

As I say, we need to see the circuit. Decoupling is pretty critical, as is PCB layout. More likely is load capacitance causing a problem - even 20pF may cause problems.

Keith