| 摘要 |
A clamp circuit and method, which are capable of increasing the dynamic range of an input image signal and minimizing line noise, are provided. A clamp circuit includes a first clamp unit, a variable gain amplifier, a second clamp unit and a clamp controller. The first clamp unit operates under a specific condition, clamps the reference input section of an analog image signal according to at least one first clamp pulse and fixes the DC bias level of the image signal to a predetermined level. The variable gain amplifier (VGA) amplifies the gain of an image signal clamped by the first clamp unit and outputs the signal whose gain is amplified. The second clamp unit operates under conditions which are not the specific conditions, clamps the reference input section of an image signal whose gain is amplified according to at least one second clamp pulse and adjusts the DC bias level. The analog-to-digital converter (ADC) converts either the output of the variable gain amplifier or the image signal clamped by the second clamp unit into a digital signal and outputs the converted signal as predetermined bit digital data. The clamp controller obtains an average value by accumulating the digital data and generates the first clamp pulse and the second clamp pulse by comparing the obtained average value with a target level. According to the present method, it is possible to increase the dynamic range of an input by removing offset showing in a gain amplifier and to minimize line noise which can be shown during the amplification of a gain, using two clamp circuits. |
