| 摘要 |
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 CDS 2 , and the signal taken out from the CDS 2 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.
|
