An LED driving circuit includes: (a) a current mirror circuit having
N-channel MOS transistors whose respective gates are connected with each
other, (b) a constant current source for supplying an LED driving current
to an N-channel MOS transistor 4, (c) an LED connection terminal,
connected with the N-channel MOS transistors, for connecting the LED, (d)
an inverter and an input-terminal respectively for inputting, to a source
of the N-channel MOS transistor, an ON/OFF signal for controlling ON/OFF
of the LED, and (e) a peaking circuit, connected with a drain and source
of the N-channel MOS transistor, for generating a peaking current used in
peaking a current flowing into the LED. With this arrangement, it is
possible to provide an LED driving circuit that easily realizes low
current consumption and high-speed emission for the LED. With such an LED
driving circuit, an optical transmitter for use in an optical fiber link
can also be realized.