Sensing device for improving the speed of image sensing

A sensing device configured to operate in a reset period, an exposure period, and a readout period, wherein the sensing device comprises:

• a first transistor, comprising a control terminal and a first terminal;
• a second transistor, coupled to the first transistor and configured to set a voltage of the control terminal during the reset period;
• a sensing element, coupled to the first transistor and configured to change the voltage of the control terminal during the exposure period;
• a third transistor, coupled to the first transistor and comprising an output terminal, wherein the output terminal is configured to output a sense signal from the first terminal during the readout period;
• and
• a readout circuit, coupled to the output terminal and comprising:
• a current mirror, coupled to the readout line;
• and
• a supplying transistor, comprising a control terminal, a first terminal, and a second terminal, wherein the control terminal of the supplying transistor receives a bias voltage, the first terminal of the supplying transistor is coupled to a supply voltage, and the second terminal of the supplying transistor is coupled to the current mirror;
• wherein the first transistor is an N-type transistor, and the third transistor is a P-type transistor.