A finite-mesh technique for laser trimming of thin-film resistors

A laser trimming technique in which a finite number of links are cut in a regular mesh of identical-valued resistors is described. The method eliminates long-term resistance drift due to slow annealing in the 'heat-affected-zone' adjacent to the laser kerf. It is shown that the precision and resolution can be comparable to those achieved with conventional methods, and that quite wide ranges (up to 4:1) of absolute values can be obtained with small meshes. A computational method for constructing a lookup table of resistor values for different cut patterns is described.<
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