| 词条 | Draft:Contact diode effect |
| 释义 |
}} When metals of dissimilar work function are in proximity, a Volta potential results, which may under some conditions approach one Volt of direct current (DC). Bringing the metals into contact produces a thin depletion region in the contact area yielding a partial diode effect producing partial rectification of alternating current (AC) signals crossing the interface. Small AC signals, of peak to peak voltage amplitude of order of the Volta potential, often exhibit significant waveform asymmetry when their positive and negative half cycles (see sine wave for reference) amplitudes are measured. This is called the contact diode effect. For analog signals in the audio frequecty range of the order of 20 Hz-20 kHz, at microphone voltage levels [https://www.kfs.oeaw.ac.at/manual/3.8/html/userguide/461.htm], of approximately 5-50 mV RMS, the contact diode effect can produce audible degredation of signal quality. Thus, when designing circuits for small AC signals, the use of dissimilar metals in the signal path should be considered with care. What might appear as common sense, again using low-level analog audio signals as example, preamplifiers and pre-preamplifiers, transformers, input and output connectors, jumpers, DIP switches and interconnection cables (e.g. RCA or XLR) made with tin or steel contacts plated with a gold alloy to improve conductivity, introduce an additional boundary layer (or layers) in the signal path and actually produce a net reduction in signal quality. See alsoElectronegativityElectron Volt (eV)Jump wireReferences[https://public.wsu.edu/~pchemlab/documents/Work-functionvalues.pdf Table of Work Functions for Metals] [https://www.stereophile.com/content/sheffield-steel-doug-sax-mastering-lab Doug Sax of The Mastering Lab used solid-silver XLR connectors after extensive listening tests as mentioned in this 1989 Stereophile article] [https://www.stereophile.com/content/cables-case-solder Partial rectification of low-level analog audio signals is mentioned in this 1991 Stereophile article] {{Electronics-stub}} |
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