The invention describes a pulse oximeter driver circuit (1) realized to drive a load (12) comprising at least a red LED light source (SR) and an infrared LED light source (SIR), which driver circuit (1) comprises a current regulator (11) realized to provide LED current (Iioad) to the LED light sources (SR, SIR) a power converter (10) realized to provide a 5 DC output voltage (LW) comprising a current regulator voltage (Un) and a load voltage (Ubad) and a feedback means (13A, 13B, 13C) realized to obtain a measure (UFB) of the instantaneous voltage drop (Un) across the current regulator (11) and to report the voltage drop measure (UFB) to the power converter (10). The invention further describes a pulse oximeter device (100), and a method of driving a pulse oximeter load (12). 10 Fig. 1
