How to enhance the bandwidth of an amplifier?

Term Q factor is mostly used as quality factor of resonator tank. Lossles resonator would have infinite Q factor.
Bandwidth of amplifier depends on it's construction or type and we need schematics to give you a usable answer.

you could start with the Bode-Fano Limit

BW and Q factor are inversely proportional to each other.Q factor must be reduced to increase bandwidth..
note : the relation is
Q= resonant frequency/bandwidth