We report a unique low-cost technique for broadband gain and noise figure characterization of erbium-doped fiber amplifiers using an amplified-spontaneous-emission (ASE) source and a tunable filter with multiple steep slopes. The filter edge is tuned in steps of 10 pm and a series of output versus input power spectral density data points are taken at a fixed wavelength. Gain and noise figure of the amplifier are obtained by extracting the slope and intercept of output versus input power spectral density. The results obtained over a 20 dB total input power range are in good agreement (within ± 0.2 dB) with those obtained using conventional spectral-interpolation technique employing multiple DFB lasers at 100 GHz spacing over the C-band. The required filter depth is about 35 dB. Our method has several major advantages: (1) Low cost, as there is no need for multiple DFB laser sources or high-speed AOM modulators and RF drivers; (2) Immune to steady-state noise in the source; (3) Can be used to characterize amplifiers with fast dynamics as its accuracy is in principle not affected by the response time of the amplifying medium.