Ramp generator including emphasis circuit and pre-emphasis circuit, operation method thereof, and image sensor device including the ramp generator

An image sensor device comprising:

• a pixel circuit configured to output a pixel signal based on an external light signal;
• a ramp generator configured to output a first ramp signal;
• a correlated double sampling (CDS) circuit configured to perform correlated sampling based on the pixel signal and the first ramp signal;
• and
• a control circuit connected with the pixel circuit, the CDS circuit, and the ramp generator, and configured to generate a first ramp enable signal, a first enable signal, and a second enable signal,
• wherein the ramp generator includes
• a ramp circuit configured to receive the first ramp enable signal during a first ramp period, the first ramp period including a first reset period and a first sensing period, and the ramp circuit being configured to output the first ramp signal to the CDS circuit;
• an emphasis circuit configured to receive the first enable signal from the control circuit and to increase a voltage level of the first ramp signal during the first reset period, based on the first enable signal;
• and
• a pre-emphasis circuit configured to receive the second enable signal from the control circuit, and to further increase the voltage level of the first ramp signal during a first pre-emphasis period in the first reset period, based on the second enable signal.

A method of operating a ramp generator, the method comprising:

• receiving a ramp enable signal, a first enable signal, and a second enable signal from a control circuit during a ramp period;
• generating the ramp signal based on the ramp enable signal, the first enable signal, and the second enable signal;
• and
• outputting the ramp signal to a correlated double sampling (CDS) circuit,
• wherein the generating of the ramp signal includes,
• generating the ramp signal based on the ramp enable signal during the ramp period;
• increasing a voltage level of the ramp signal based on the first enable signal, during an emphasis period in the ramp period;
• and
• further increasing the voltage level of the ramp signal based on the second enable signal, during a pre-emphasis period in the ramp period, and
• wherein a length of the pre-emphasis period is shorter than a length of the emphasis period.