Abstract: A transmitter employing a light-emitting diode as an output element, this element being included in series with a resistor in the output circuit of a difference amplifier the inverting input of which is coupled to the junction point of the diode and resistor, includes a network for compensating for the non-linear output power versus energizing current characteristic of the diode. This network comprises a field effect transistor (fet) biased to operate in the pre-pinch-off region and having its source-drain path connected to the diode. The source-drain path of the FET may shunt the diode and a further resistor in series therewith, or alternatively may be included in a feedback path to the inverting input of the amplifier.