Glossary a To F > 자유게시판

The behavior of the first circuit - known as a half-wave rectifier - should be fairly clear: the diode conducts, and therefore creates a voltage across the resistor (a dummy load), only if the first input is more positive than the other; in this circuit, diode breakdown voltage is selected high enough not to interfere with this process. The function of this diode is to begin conducting, due to the breakdown effect, when the terminal voltage gets dangerously high. Folded dipole - The terminal impedance of a folded dipole is four times that of a simple dipole of about the same dimensions. It can be alternatively fixed by adding a large pull-down resistor from the gate to the ground, to dissipate the deposited charge when the switch is opened, but at the expense of lowering input impedance. This negative voltage will prevent that MOSFET from turning on until the charge is dissipated through the voltage divider (which takes time proportional to the capacitances and resistances involved) - and the gate is positive enough again. Because of this, almost all modern computers use global clock signals to ensure that all operations are properly synchronized, and all circuits are allowed enough time to reach the expected output state.

The output waveform from a rectifier has non-zero average DC voltage, though - corresponding to the amplitude of the input signal (shown below in green in the graph below). 3V. This circuit is shown in column B above. This bias-compensated, DC-coupled voltage follower is shown in column C above; try to think for a moment about how it works in practice - and observe that the arrangement of transistors is opposite to that in a push-pull switch. Column C shows another arrangement that is not universally problematic, but should be avoided in switching where possible - and is all-too-common in hobbyist work: loading the emitter (BJT) or drain (MOSFET) - a configuration known as "common collector" or "common source". Also note that the upper transistor, connected to the positive rail, is PNP or p-type MOSFET; and the bottom one, grounded, is NPN or n-type MOSFET. The second circuit - a bridge or full-wave rectifier - is a bit more clever, but also easy to follow: opposing pairs of diodes are used to select the more positive or negative out of two input leads, and always produce a particular output polarity. When the voltage is close to the positive rail, the situation will reverse; in effect, this arrangement is an inverting switch.

The tendency for diodes to maintain a precise voltage drop across their terminals is often exploited to provide precise voltage references in a circuit. Forward-biased diodes, with their 0.2 - 0.7V voltage drops, are usually less useful; but reverse-biased Zener diodes are a wholly different story. Forward-biased diodes serve a number of useful functions of their own. Diodes are also commonly used to build constant-current sources, such as this circuit: this arrangement will admit only as much current as needed to create a particular voltage across the constant "sense" resistor, R2, regardless of the potentially variable voltage drop seen across the connected load. The key advantage of this design is that it wastes less energy (although it still wastes it in proportion to the load current and the desired voltage drop). Coal plants churn out carbon dioxide in vast quantities, and are even more radioactive than nuclear plants, but lack of public understanding means they are more popular still and therefore it may well be political suicide to throw your weight behind nuclear power. If you have any questions or anything feel free to reach out! When sizing a solar panel for a direct solar system, you only have to look at power production.

I need a bigger grommet for the laptop's power cable where it exits the panel, too, since I can see daylight around it! See "Nulls in radiation pattern". In all cases, the driving voltage applied to the base (or gate) must be high enough to trigger the transistor; that is, at least 0.6V in BJT, and at least 1-2V for most MOSFETs. 700 watts), so I doubt I’ll want to shell out for a solar system big enough to power the one in my kitchen. The simplest type of switch has one input and one output ("single-pole, single-throw", or "on-off" switch). Another important and more subtle use of these semiconductor devices is amplification, however - modulating output signals in relation to input voltage or current. The resistor on diode side should be selected to limit the current through the diode to a reasonable value, so that it has an opportunity to develop a voltage across its terminals in the first place, but so that it does not waste too much power. The most unsophisticated use of a diode is a shunt; shunts may be placed across the terminals of high-impedance, low-precision signal sources to trim the voltage to a particular level; or to suppress transient voltage spikes caused by inductors, electrostatic discharge, or even lightning strikes (using a specialized varistor diode).

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