CHAPTER 2
Passive Components Electronic components are the building blocks of an electronic circuit, and all electronic circuits are created by joining components together. At one time this was done by soldering wires between the terminals of components, but nowadays the connections are more likely to be made using metal tracks on an insulating board (a printed circuit board or PCB). On a PCB holes are drilled into the metal tracks, so that components located on the insulated side can be attached and connected by pushing their connecting wires through the holes so that the wires can be soldered to the metal track. We will come back to that in Chapter 5. Often now both the connections and the components are all contained in a single piece of silicon, the integrated circuit (IC), which we shall look at in Chapter 3. In such a circuit, both steady and alternating voltages will exist together, and several types of components do not behave in the same way to alternating voltages as they do to steady voltages. In addition, components can be active or passive. Active components are used to copy (amplify) waveforms and to switch voltages and currents on and off under electrical control. Such active components need an input signal (a waveform) to control an output signal, and they also need some source of power, which is usually a steady voltage supply. A circuit that contains active components can produce an output waveform which provides more power (voltage multiplied by current) than its input waveform. In other words, active components can provide amplification of power. n
Note There are passive components, such as transformers, that can provide amplification of voltage (but at reduced current) or amplification of current (at reduced voltage), but not amplification of power. n
Passive components always reduce the power of an input waveform, so that an output wave from a circuit that contains only passive components is always at a lower power than (or the same power as) the input. Passive components do not need any additional steady voltage supply to enable them to deal with waveforms. A complete electronic circuit will normally consist of both active and passive components, arranged so that the passive components control the action of the active components and act as a path for signal waveforms. Take a look now at the most common passive components, resistors, capacitors, and inductors. Electronics Simplified. DOI: 10.1016/B978-0-08-097063-9.10002-0 Copyright Ó 2011 Ian Sinclair. Published by Elsevier Ltd. All rights reserved.
23