This depends on the frequency you need to operate, because the gain (Av) bandwidth (fh) product of the op amp is a constant: K=Avfh, where Av is the open-loop gain of the op amp, the ordinary op amp can reach 10^6, fh is the upper limit frequency of the op amp, the ordinary op amp is about 10Hz, then K=10^7 in the case of meeting the actual operating frequency f, the maximum amplification gain can be achieved: Avmax=K\/f.