Goa driving cicuit and lcd device

A liquid crystal display (LCD) device, comprising a gate driver on array (GOA) driving circuit, wherein one cycle of the GOA driving circuit comprises a first interval and a second interval, the GOA driving circuit comprises a plurality of cascaded GOA units and outputs a gate driving signal to an Nth-stage horizontal scanning line of a display region by an Nth-stage GOA unit, the Nth-stage GOA unit comprises a pull-up unit, a pull-up control unit, a pull-down unit, a pull-down sustaining unit, a download unit, and a bootstrap capacitor unit;

• the pull-up unit, the pull-down unit, the pull-down sustaining unit, and the bootstrap capacitor unit are respectively electrically connected with a first node and an Nth-stage horizontal scanning line, the pull-up control unit and the download unit are electrically connected with the first node, wherein N is a positive integer;
• wherein the pull-down sustaining unit comprises a sixth thin film transistor (TFT) and a seventh TFT;
• a source electrode of the sixth TFT is electrically connected with the first node, a drain electrode of the sixth TFT is connected with a first low level, a gate electrode of the sixth TFT is connected with a second node;
• a source electrode of the seventh TFT is electrically connected with the Nth-stage horizontal scanning line, a drain electrode of the seventh TFT is connected with the first low level, and a gate electrode of the seventh TFT is electrically connected with the second node;
• in most of the first interval, threshold voltages of the sixth TFT and the seventh TFT are forward biased;
• the Nth-stage GOA unit further comprises a negative bias unit for negatively biasing the threshold voltages of the sixth TFT and the seventh TFT in the second interval.