Monolithic circuit technology has recently been proliferating in the field of active matrix display devices. This technology involves forming, on the same glass substrate, pixel TFTs (thin film transistors) for controlling the application of electric charge to the pixels, and peripheral circuit TFTs that form a portion of a driver circuit or the like.
The abovementioned TFTs, however, have fluctuations in the threshold voltage for switching operation of the TFTs due to voltage stress applied to the gate electrodes, and this is known to cause characteristic degradation of the TFTs. Patent Document 1, for example, discloses a double-gate structure TFT having back gates, and when such characteristic degradation occurs, the drive circuit applies a control voltage of the same polarity as the fluctuation in threshold voltage to the back gates, thereby compensating for the fluctuation in threshold voltage.