A photospectrometer has been realized in a standard integrated circuit (IC) process. Only the masks, materials, and fabrication steps inherent to this IC process were used (i.e., no post processing to add mechanical or optical devices for filtering). The spectrometer was composed of a set of 18 photodetectors with independent spectral responses. The responses of these devices were weighted and summed to form outputs proportional to the input optical power in discrete wavelength bands in the region from∼400to∼1100 nm.With the solution space restricted to a 60 nm band, this instrument could resolve Gaussian input spectra(&sgr;=5 nm)with a peak-to-peak spacing of less than 15 nm. This device could easily be integrated with additional analog, digital, or wireless circuits to realize a true laboratory instrument on-a-chip. ©1998 American Institute of Physics.