LTC6268
Recommended for New Designs
The LTC6268/LTC6269 is a single/dual 500MHz FET-input operational amplifier with extremely low input bias current and low input capacitance. It also features...
Datasheet
LTC6268 on Analog.com
LTC6269
Recommended for New Designs
The LTC6268/LTC6269 is a single/dual 500MHz FET-input operational amplifier with extremely low input bias current and low input capacitance. It also features...
Datasheet
LTC6269 on Analog.com
The Datasheet specifies that the GBW is 500MHz but
the datasheet also specifies that -3dB bandwidth at A = 1 is 350MHz,
and in page number 9 the Gain and Phase vs Frequency graph 
The frequency at gain = 0dB is about 300MHz and 400MHz respectively
So when I am designing a TIA using LTC6268/LTC6269 what should I consider the GBW of this IC as?
Hi Agumbe: the 500MHz Gain Bandwidth Product is specified at 10MHz. That means the open loop gain at 10MHz is 50. The number you would use in your calculations depends on what bandwidth you are trying to achieve. If you are trying to achieve medium high bandwidths like 10MHz, then use the higher number. But if you are targeting high bandwidths, use the lower number.
Stabilize Your Transimpedance Amplifier This article by Analog Devices has the design for a TIA for photodiode, see Fig. 5
What should I take fGBWP as 350MHz or 500MHz?
I am trying to design TIA for a photodiode for 10MHz bandwidth -3db BW