| 摘要 |
A FIRDAC (20) is described, coupled to a noise-shaper (12) with a DC offset. The resulting offset of the FIRDAC itself is compensated by a compensation current source (Pcomp; Ncomp) which is continuously ON.The FIRDAC has a plurality of FIRDAC cells (40), each cell comprising at least one current source (50; 70). In a FIRDAC cell having a relatively small current source, a dummy transistor (80; 90) is formed in the free space. The compensation current source is formed as a parallel combination of certain dummy transistors.In a possible embodiment, each FIRDAC cell (40) comprises a stack comprising a D-flipflop (60), a PMOS current mirror (50) above the flipflop, and an NMOS current mirror (70) below the flipflop. In a cell with relatively small PMOS and NMOS current mirrors, a dummy current mirrors (80; 90) are formed in the substrate (100). A plurality of these dummy current mirrors (90; 80) are connected in parallel to constitute said compensation current source (Ncomp, Pcomp). FIG. 4.
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