CDS-1402

The CDS-1402 is an application-specific, correlated double sampling (CDS) circuit designed for electronic-imaging applications that employ CCD's (charge coupled devices) as their photodetector. The CDS-1402 has been optimized for use in digital video applications that employ 10 to 14-bit A/D converters. The low-noise CDS-1402 can accurately determine each pixel's true video signal level by sequentially sampling the pixel's offset signal and its video signal and subtracting the two. The result is that the consequences of residual charge, charge injection and low-frequency "kTC" noise on the CCD's output floating capacitor are effectively eliminated. The CDS-1402 can also be used as a dual sample-hold amplifier in a data acquisition system.

The CDS-1402 contains two sample-hold amplifiers and appropriate support/control circuitry. Features include independent offset-adjust capability for each S/H, adjustment for matching gain between the two S/H's, and four control lines for triggering the A/D converter used in conjunction with the CDS-1402. The CDS circuit's "pingpong" timing approach (the offset signal of the "n+1" pixel can be acquired while the video output of the "nth" pixel is being converted) guarantees a minimum throughput, in a 14-bit application, of 5MHz. In other words, the true video signal (minus offset) will be available