Inductive kick

So if, for example, the source-to-ground trace is a little too long, it can generate a significant inductive kick at the instant of a switch transition that can at best slow down the transition somewhat, or at worst, produce spurious (unintended) turn-on and turn-off of the Fet, leading to its destruction. 

Note that while prototyping, it is a bad idea to insert a current probe (through a loop of wire), anywhere in a critical trace section. The current loop becomes an additional inductance that can increase the amplitude of the noise spikes dramatically. Therefore practically speaking, it can often become virtually impossible to measure the switch current or the diode current individually (especially in the case of switcher ICs). In such cases, only the inductor current waveform can really be measured properly. Sometimes we can place a small sense resistor instead of a current loop, because a good resistor will not create inductive kicks at least. 

Inductive kick A voltage surge produced when a current flowing through an inductance is interrupted. Inductive load A load that possesses a net inductive reactance. 

Instead of an introductory chapter that presents a mass of text about the history of electronics, or its importance in modern life, this chapter will start right in with experiments illustrating the "inductive kick" that sometimes destroys expensive computers. These experiments also include making a simple radio transmitter of the type that saved 600 people on the ship Titanic. 

Figure 1.3 Using the inductive kick to light a neon bulb.

AM ("amplitude modulation") is sensitive to this type of "radio frequency interference," or RFI. There are so many different kinds of electrical machines generating inductive-kick RFI, that AM radio reception in a crowded city environment is plagued by background noise, which is usually called "static." Set the radio to FM ("frequency modulation") and repeat the experiment. FM is far less sensitive to RFI, and this is one of its biggest advantages over AM. 

Switching the MODE from CH2 to DUAL and TIME/DIV from X-Y to 20 ms will provide a two-wave display, much like the right-hand side of Fig. 9.7. (Unplug the BNCs before the transformer, to avoid an inductive kick.)... 

If the relay has a transparent case, sparks can be seen at the NC contacts, and this would eventually damage them, if the experiment were continued for a long time. The inductive kick of the coil is not allowing the current to stop very fast. 

On pages 110 and 138, capacitors were used as snubbers, to absorb the inductive kick from a quickly tumed-off inductor. Another way to do this is to attach a PN diode, not across the switch as on page 138, but across the coil, as in Fig. 14.10. 

A useful avalanche diode that works in either direction is the "varistor," sometimes called the "metal oxide varistor," or "MOV." It is not just a single crystal device as the previously described semiconductors are, but instead it is polycrystalline ceramic material, usually zinc oxide, with many small PN junctions at the grain boundaries. It is quite inexpensive and is very rugged, so it can be found as an important part inside most "surge protector power strips" for connecting multiple computer modems, printers, etc., to protect them against inductive kicks and even most "spikes" ("transients") from lightning. ... 

A capacitor plus resistor (usually both of small values), which is arranged to catch "inductive kick" voltage pulses and harmlessly short circuit them. Another way to do this is with a rectifying diode. Still another way is with a Zener diode or argon gas tube. 

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