| 摘要 |
A diffused semiconductor resistance structure has a resistance value that is practically independent of applied voltage. The structure includes an isolation layer 22 diffused into an underlying substrate 12, a resistance layer 20 diffused into the isolation layer, and a conductive element 30 connecting the isolation layer to an electrical contact 28 near the midpoint of the resistance layer. The junction between the resistance layer and the isolation layer is thereby zero-biased at its midpoint, is forward-biased on one side of the midpoint, and is reverse-biased on the other side of the midpoint. Consequently, the average thickness of a depletion region formed at the junction, and the average effective depth of the resistance layer, are maintained constant and practically independent of applied voltage, to provide a resistance value that is also practically constant. Undesirable high forward bias voltage allows the junction between the isolation layer and the resistance layer is avoided by connecting the diffused semiconductor resistance structures in series. The series connected arrangement may be used in a monolithic digital-to-analogue converter. <IMAGE> |
