gipo
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Hi there. I would start using a classical 2 stages Miller Opamp. 1. the Gain-Bandwidth is well controllable: gm,in/Cc, but you must have a high current consumption budget to get 500 MHz; 2. the open loop phase response has the minimum number of extra poles/zeros others than dominant, non-dominant poles and RHP zero; in a cascode topology the high frequency poles might likely fall at frequencies close to 500 MHz (depending on the process), thus compromising the opamp's stability; watch out your feedback network, which might likely add extra poles at the frequencies of interest, in the open loop AC response, influencing then the stability; 3. the output swing is the widest available and a good linrarity can be expected; 4. a 50-60 dB DC gain can be easily accomplished, depending on the load impedance.
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