Digital Automatic Gain Control Circuit
Original Publication Date: 1984-Nov-01
Included in the Prior Art Database: 2005-Feb-05
This article describes a digital automatic gain control (AGC) circuit used in a CCD (charge-coupled device) image sense circuit, in which a gain is so controlled that a peak value of output voltage is regulated to a reference value. The circuit includes an analog/digital (A/D) converter which operates as a divider. Fig. 1 shows the concept of the digital AGC circuit. The CCD sensor 1 includes photodiode elements arranged in the direction of width of a document 2. The CCD sensor senses the image of the document in the direction of its width. As the CCD sensor array 1 moves relative to the document 2, the CCD sensor array 1 generates analog signals of successive scan lines. The analog signal is applied to the digital AGC circuit 5 through a pre-amplifier and a sample hold circuit 4.