a display driving circuit having a shift register is formed on the display panel . the shift register includes a first stage having first and second transistors and a second stage having a third and fourth transistor . a voltage of a control electrode of the first transistor is boosted by a voltage of a first pulse line changing from low to high . in an on state , the second transistor connects the control electrode of the first transistor and a constant voltage line . a voltage of a control electrode of the third transistor is boosted by a voltage of a second pulse line changing from low to high . in an on state , the fourth transistor connects the control electrode of the third transistor and a constant voltage line . the fourth transistor is switched on by a signal from the first stage .