Editing Diode (section)

===Small-signal behavior===
At forward voltages less than the saturation voltage, the voltage versus current characteristic curve of most diodes is not a straight line. The current can be approximated by <math>I = I_\text{S} e^{V_\text{D}/(n V_\text{T})}</math> as explained in the [[Shockley diode equation]] article.

In detector and mixer applications, the current can be estimated by a Taylor's series.<ref name="Giacoletto_1977">{{cite book |author-first=Lawrence Joseph |author-last=Giacoletto |title=Electronics Designers' Handbook |location=New York |publisher=[[McGraw-Hill]] |date=1977 |pages=24–138}}</ref> The odd terms can be omitted because they produce frequency components that are outside the pass band of the mixer or detector. Even terms beyond the second derivative usually need not be included because they are small compared to the second order term.<ref name="Giacoletto_1977" /> The desired current component is approximately proportional to the square of the input voltage, so the response is called ''[[square-law detector|square law]]'' in this region.<ref name="HC" />{{rp|p. 3}}