Do u mean a DC amplifier or a hi current supply>? Or perhaps a signal amplier ?
If it's under 20ma output drive I'd suggest using an opamp, for lower freq. u can go with an LM258/358 as those are single rail and will give u 3.3V out from a 5V supply. 200Khz should be ok for them, but check the spec sheet to be sure. Just setup the feedback to give u the 1:3.3 amplification.
If u are dealing with just the signal out, place a decoupling cap on the input & output. Perhaps a .1uf should work ok at those freq.