J. Kodama, H. Fujimoto, and J. Ishii (Japan)
Multi-layer distributed RC line; Sallen-Key circuit; Active filter, Trimming
The trimming effect of a distributed RC multi-layer line incorporated into the Sallen-Key circuit, which is convenient for obtaining Butterworth or Chebyshev characteristics, is investigated numerically. Using a 4-layer distributed RC line in the Sallen-Key circuit, the descent of the gain-frequency characteristic becomes steeper than that of a 2-layer distributed RC line or a normal Sallen-Key circuit. The cut-off frequency shift achieved through trimming becomes large in order of rectangular, exponential and linear shape. As an adjustment method for the quality factor changes brought about by trimming, adjustment for feedback capacitance is useful. For the practical fabrication of a desirable active filter and adjusting a cut-off frequency, it is recommended that only the resistance film inside the multi-layer distributed RC line be trimmed.
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