I am planning to use a differential amplifier, LTC6409 which is reported to have a GBW of 10GHz. I ran an AC analysis on LTSpice using the Spice model given here. I connected the negative input to ground and the positive input to an AC source. The result shows that the open loop gain reaches 0dB at around 2GHz. The open loop gain at 10GHz is around -27dB.
As far as I understand, I can add feedback and have a flat close loop gain of 0dB up to 2GHz, but it is not possible to have a closed loop gain of more than 0dB beyond 2GHz.
Now I thought of three possibilities
- My simulation or my understanding of the concept of GBW is incorrect.
- The Spice model of the op-amp is incorrect
- The reported GBW is incorrect (I hope not!)
Can anyone please help me understand this? Any suggestion for other differential amplifiers with GBW of at least 5GHz would be great.