Improvement of laser trimmed film resistor stability by selection of optimal trim paths

A study comparing post-trim drift performance of laser-trimmed film resistors is presented. The goal was to determine the influence of the following factors on post-trim drift performance: (1) type of trim cuts, (2) initial trim position, (3) laser adjustment parameters, and (4) amount of trim. Based on these, simple design guidelines for improved resistor stability were derived. The study is based on computer simulations. Simple rules of thumb to optimally trim film resistors are derived. With these rules post-trim drift of film resistors can be reduced by as much as a factor four.<
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