Patent attributes
The present invention relates to an analog front end circuit which is preferably used for taking out an image signal from a charge coupled device, that is used as image pickup means in an electronic camera such as an electronic still camera, a video camera and the like. In the present invention, an image analog signal which is produced by, for example, the charge coupled device (CCD: not shown) is supplied to a correlated double sampling circuit (CDS) 2 through an input terminal 1. The image analog signal is taken out through the CDS2, and the signal taken out from the CDS2 is supplied to an analog type programmable gain control amplifier (PGA) 4 through a changeover switch 3. Either the gain controlled signal by the analog PGA 4 or the signal sent from the changeover switch 3 is selected by a changeover switch 5. The selected signal is further supplied to, for example, a 12-bit analog digital converter (ADC) 6. The converted digital signal is supplied to a digital type programmable gain control amplifier (PGA) 7 comprised of, for example, a multiplier and is then taken out from an output terminal 8. In this manner, the noise generation and power consumption under occasional use conditions can be minimized.
