An integrated optic device is described which acts as the optical analog of a voltage regulator or, more precisely, a tunable voltage source. This device is suitable for stabilizing a fluctuating optical intensity or for providing a tunable power source with immunity to input power variations. An incoming optical signal is beamsplit by a tunable directional coupler (the control element), the output channel of which is further sampled by an additional coupler (the monitor element) and the intensity is compared to a reference level. The resulting error signal, suitably amplified, serves to adjust the first coupler, driving the output intensity to the reference level in a negative feedback loop. The design and performance of a device fabricated in Ti-indiffused lithium niobate is discussed.