OPA855: Opamp Simulation issue

Unity Gain? Maybe you are input limiting? 

Yes, I am considering unity gain.I am providing 2.5V input offset also.So the input will be Low =0V and High =5V

Well 1st the OPA855 is not unity gain stable so that is the ringing you see at gain of 1, oscillating, 

And 2nd, the input pins require a headroom to the supply, that is the clipping you are seeing, looks like 2.1V headroom to the V+ supply and 1.1 to the negative supply - usually not an issue if you are operating above the min gain of 7V/V or running inverting, 

Hi,

It is not a rail to rail amplifier, so you need to provide higher supply atleast 6V to work for 5V signal. and this is a high bandwidth amplifier so at unity gain it will have 8Ghz of bandwidth which will make this unstable or add some ringing in the output. This amplifier is mostly used in transimpedance application. what is your requirement? why you need such a high bandwidth amplifier?

Regards,

Rohit

Hello Rohit,

Thanks for your feedback.

I want to use a buffer on the USB D+/- lines. The max data transfer will be 480Mbps. Could you please suggest any buffer?

Regards,

Tensil Seabastian

Hello Micheal,

Thanks for your valuable input.

Regards,Tensil Sebastian

Then do you need FDA?

what is FDA

Hi Sebastian,

do you want to connect your buffer to an existing USB line with regular USB interface chips connected at both ends? And do you want to connect such a buffer to both single lines? Or do you want to build a receiver as can be seen in an USB interface chip?

In the first case, a comparator could do. Take care that you don't add too much impedance to the line. Otherwise the line termination is ruined.

In the second case, you would need to take an amplifier with an differential input. And you would need to carry out the proper line termination. But for this case special USB interface chips are sold.

By the way, a "FDA" is a "fully differential amplifier", with differential inputs and differential outputs.

Kai