How to make a small amplifier, able to amplify a signal 2 × the input
You can use a good video op-amp to do this. Eg. AD8047/8 (GBW = 160MHz), provided your output load is 75\$\Omega\$ or greater. 



The AD8047 is shown, which is stable at a gain of 1, so it's less likely to break into oscillation with a gain of 2. You'll note that the phase difference between input and output at 8MHz is fairly small. The AD8048 would be better in that respect.