Triple wavelength LED driver for optical brain-computer interfaces

A dedicated triple wavelength LED driver is presented for optical brain-computer interfacing (BCI). The solution caters for the constraints of a common-anode grounded case and modulation up to several kilohertz that allows source separation of light that has back-scattered from the brain. With total harmonic distortion of 0.95- and a frequency range of ~40-kHz, the driver has application in a continuous wave optical BCI. Other modulation strategies such as time division multiplexing (TDM) are catered for, owing to input DC coupling. Linearity in the optical output is maintained by the -load sensing- differential op-amp on the LED-s current limiting resistor, which is the basis for the V-I conversion.