An apparatus for digitizing an analog electrical signal comprises a linearized sampler having an analog electrical input and a sampling input, a bandpass filter having a center frequency of at least half of the quantization rate of a quantizer in communication with the sampler, and the quantizer in communication with the bandpass filter. The linearized sampler in one embodiment is a linearized optical modulator with an optical input. The sampler frequency in another embodiment is chosen such that second-order distortion products generated in the sampler are separated in frequency from the sampled input band.