Shift register with low stress
A shift register includes a plurality of register stages. Each register stage includes an output circuit, a first switching circuit and a second switching circuit. The output circuit is capable of outputting a first driving signal. The first switching circuit is used to pull down the output circuit into a low voltage level when the output circuit is not outputting the first driving signal. The second switching circuit is capable of receiving an input signal. The first switching circuit holds electric charges by the parasitical capacitor resident in the transistor in order to keep the first switching circuit in a turn-on state when the output circuit is not outputting the first driving signal.
1. A shift register comprising:
an output circuit ( 36 ), comprising:
a first transistor (T 2 ) for receiving a first clock signal and outputting a first driving signal; and
a second transistor (T 6 ) for pulling down a voltage level of an output end of the first transistor to a low voltage level when the first transistor does not output the first driving signal;
a first switch circuit ( 52 ), comprising:
a third transistor (T 1 ) comprising a drain, a gate and a source, the drain and the gate of the third transistor being coupled to a second driving signal, the source of the third transistor being coupled to a control end of the first transistor;
a fourth transistor (T 5 ) comprising a gate and a drain, the gate of the fourth transistor being electrically connected with the second transistor, and the drain of the fourth transistor being electrically connected with the control end of the first transistor, for pulling down a voltage level of the control end of the first transistor to the low voltage level when the first transistor does not output the first driving signal; and
a fifth transistor (T 8 ) comprising a gate and a drain, the drain of the fifth transistor being coupled to a second clock signal, for receiving a first input signal for controlling the turn-on/turn-off states of the second and the fourth transistors; and
a second switch circuit ( 34 ), comprising:
a sixth transistor (T 3 ) comprising a source, a gate and a drain, the gate and the drain being electrically connected to a second input signal, the source of the sixth transistor being electrically connected to the gate of the fifth transistor;
wherein the second and the fourth transistors store charges in parasitical capacitor thereof by a voltage level of the second input signal for keeping the voltage levels of the gates of the second and the fourth transistors in a high voltage level, the second and the fourth transistors are kept in the turn-on state when the first transistor does not output the first driving signal.
2. The shift register of claim 1 , wherein the second switch circuit further comprises a seventh transistor (T 4 ) for turning off the second and the fourth transistors when the first transistor outputs the first driving signal.
3. The shift register of claim 1 , wherein the low voltage level approaches a ground voltage.