Highly saturated, erbium-doped fiber amplifiers can be employed as efficient power amplifiers. Differential pump-to-signal conversion efficiencies of 59%, (quantum-efficiency of 93%) can be obtained, resulting in 54 mW (+ 17.3 dBm) of amplified signal for only 100 mW of pump power at 978 nm. In addition, these amplifiers are shown to have virtually-flat spectral-gain characteristics with a 1 dB bandwidth in excess of 38 nm.