Patent ID: 7414552

Claim:
An analog front end circuit converting an analog signal outputted by an image sensor into a digital signal, the analog signal comprising a first voltage level signal and a first reference signal, the analog front end circuit comprising: a sample and hold circuit comprising: a variable gain amplifier circuit comprising a first input end, a second input end, and at least one output end, the first input end being used for receiving the first voltage level signal, the second input end being used for receiving the first reference signal, the output end being used for outputting at least an amplified signal, a first sample switch in the front end of the first input end, a second sample switch in the front end of the second input end, and a hold switch connected between the first input end and the second input end, wherein the first sample switch and the second sample switch are both controlled by a sample pulse signal, wherein while the first sample switch is at a first conductive state, the first input end receives the first voltage level signal, while the second sample switch is at the first conductive state, the second input end receives the first reference signal, and while the hold switch is at a second conductive state, the output end outputs the amplified signal; and an analog to digital converter device for receiving the amplified signal and converting the amplified signal into the digital signal.