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The Unity Gain Bandwidth can sometimes be larger than the GBP if there is peaking in the circuit. If you look at the datasheet table on the OPA842, the G=1, Rf=25 Bandwidth =350MHz, G=2 BW = 150MHz, For gains of 5 and greater the GBW is around 200MHz. Remember that the amplifier gets more stable as the gain increases, which means that the phase margin is starting to increase. As the phase margin increases, the BW tends to reduce.
