How to change GBW in ADA4627-1 Spice macromodel ?

Hi everybody,

I am currently trying to build a photodiode transimpedance amplifier based on the ADA4627-1 opamp. The first result I have obtained on a prototype circuit are quite bad, as I get a lot of excess noise generated inside the circuit.

I think that the abnormal behavior of my circuit may come from the tolerance on the opamp GBW Product. The datasheet specify a GBWP of 19 MHz, with a minimum guaranteed value of 16 Mhz. As I have designed the circuit using the 19 MHz GBWP value, my hypothesis is that I have a real opamp that is slower, with a real GBWP between 16 MHz and 19 MHz.

Now I would like to test that in Spice by simply changing the value of the GBWP product of the ADA4627-1 macromodel. However, I have no idea about how to do that, and the ADA4627.cir file don't help me, since the GBWP parameter is not explicitly specified.

So, here is my question: how to change the GBW product of the ADA4627 macromodel ?

Thank you very much for any help.

  • 0
    •  Analog Employees 
    on Jun 28, 2016 12:42 AM

    Hello Richard,

    I simulated the closed-loop gain of the ADA4627 at unity gain and got a -3dB frequency at about 23MHz. You could try and simulate with the amplifier in a buffer configuration and see what bandwidth you get to have an idea, and then simulate your circuit to test out your theory.

    Could you provide your schematic? How would you describe the noise you are seeing? If you could provide some scope shots or some details about your observations, that would help in identifying the problem.