Voltage followers may sound boring, but they are immensely useful in electronic circuits; for example, they can be used to bridge a significant number of RLC band-pass or band-stop filters, or to convert very faint high-impedance currents from external sensors into outputs suitable for other circuitry. Many other RLC circuits can be designed, although these two approaches are most useful when easily understood dependence on source and load impedances is required. An unexpected low-pass filter distortion seen in a digital signal is usually indicative of excessive capacitance of the signal path, perhaps because the connection is too long, or runs too close to others; while a high-pass pattern may indicate a broken trace or cut wire, forming an unwelcome capacitor in series with the source of the signal. The action of a capacitor in parallel with a load appears to be reminiscent to the behavior of a series inductor. As with RC and RL filters, the gotcha with RLC circuits is that in signal processing, the impedance of the driven load must be significantly higher than that of the signal source and the series resistor in the circuit - or else, distortion will appear. In both these cases, a more sophisticated, active circuit - implementing a "real" current source - is necessary instead.

This circuit is, therefore, a simple, passive low-pass filter. I²R) will also be negligible - around 1/8 watt; for higher currents, the amount of dissipated heat goes through the roof pretty quickly, though - and therefore, resistor-based current limiters are useful only in low-power uses. However, the magnetic coils and higher intermediate conversion frequencies in DC-DC converters and charge controllers (especially if these are less reputable "I-just-found-this-on-the-internet" products) may be tricky, so also keep these away from your head. The difference is that the smaller the resistor, and the larger the capacitor, the lower output impedance the filter will have - but the more power it will keep wasting, and the lower the impedance of the driving signal source would need to be to avoid distortion. As the frequency increases, however, the signal will get more and more attenuated - and the phase shift will become greater - as the source can't charge or discharge the capacitor quickly enough. 5RC, the capacitor will be more than 99% charged, with almost no current flowing - and a voltage equivalent to that of the power source will be present across its terminals. Thankfully, we can prevent this current from flowing in a very simple way.

In practice, the optimal way to design an RLC band-pass filter is to pick R to achieve the desired output impedance; continue with L for the desired bandwidth; and finally, C to set the center frequency. To build this circuit in practice, we can safely use use the nearest "preferred" resistor value, 330 Ω (which would actually allow 21.5 mA to flow through the device - well within the safety limits of most components). If the resulting flow of charges is slow enough, they will simply drain through the resistor; but if the rate of change is very high, the resistor will limit the current, and develop a substantial, momentary voltage difference across its terminals. There is one key difference inductors oppose changes in current for a longer time when the current is higher; whereas a capacitor has a more pronounced effect when the current that charges or discharges it is lower; were we to eliminate the upstream resistance, the capacitor would charge instantaneously.

With the cables underground and in ducts, there will of course be a smaller risk of them being damaged by storms or accidents. This includes electrical wires for residential and commercial use, communication cables, power cables, and specialty cables like fire-resistant cables. Electrical incidents such as overheated wires or fires can cause significant property damage. Inductors can replace capacitors in RC filters, reversing their operation: an RL filter with the same topology as an RC low-pass filter will act as a high-pass filter, and vice versa; the reason for this should be fairly evident. This circuit passes higher frequency sine wave signals largely unaltered, but attenuates slow-changing sine waves - a high-pass filter. Note that these circuits work as expected only for sine waves (and in such a case, will output a sine wave, too). A variety of resistor-capacitor-inductor arrangements can be used to form circuits with interesting frequency response characteristics. The most common is extremely thin wires, which can sometimes lower the conductivity and capacity. The circuits in the A column show common, proper transistor switch arrangements for NPN, PNP, and MOSFET n-channel enhancement mode transistors - known as "common emitter" (BJT) or "common drain" (FET).

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