Analog-to-digital converter and image sensor including the same

An image sensor comprising:

• a pixel array including a plurality of active pixels;
• and
• an analog-to-digital converter (ADC) configured to convert a pixel signal of the plurality of active pixels into a digital signal,
• wherein the ADC includes:
• an input circuit configured to receive a ramp signal and the pixel signal, and configured to output a first signal in which the ramp signal is applied to the pixel signal;
• an inverter including a pull-up transistor and a pull-down transistor connected in series between a power supply node and a ground node, the inverter being configured to output a second signal obtained by inverting the first signal input through an input node to an output node;
• and
• a code generation circuit configured to output the digital signal based on the second signal, and
• wherein the inverter includes at least one starving transistor configured to limit a magnitude of a current flowing through at least one of the pull-up transistor and the pull-down transistor during a transition operation of the inverter.

An analog-to-digital converter (ADC) comprising:

• an inverter including a P-type pull-up transistor and an N-type pull-down transistor, which are connected in series with each other through an output node between a power supply node and a ground node and have gate electrodes connected to an input node, the inverter being configured to output a second signal obtained by inverting a first signal input through the input node to the output node;
• and
• a code generation circuit configured to output a digital signal based on the second signal,
• wherein the inverter includes at least one bias transistor connected in series with the N-type pull-down transistor between the N-type pull-down transistor and the ground node and configured to be controlled by a bias voltage.