The characteristics of novel optical bistable devices which integrate both interdigital electrodes and amorphous silicon photovoltaic detectors on the Ti-diffused LiNbO3 waveguide are described. In the devices, the transmitted light of the interdigital electrodes enters the amorphous silicon photovoltaic detectors and the output voltage of the detectors is fedback to the electrodes. Optical bistable operation occurs due to the nonlinear dependence of the transmission efficiency of the electrodes on the applied voltage. The characteristics of differential gain and hysteresis of the device were observed experimentally.