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Chapter 4 Linear Circuits > Power and Root Mean Square Values - Pg. 74

74 Chapter 4 of current through the tuned circuit, the voltage across the tuned circuit will be a complete wave even if the transistor stops passing current for part of the time. Summary Tuned amplifiers use resonant circuits tuned to a particular frequency, and the circuits can be arranged to give whatever bandwidth is required. Quite simple circuits can provide narrow bandwidths, but for wide bandwidths or several megahertz more elaborate designs are needed. Power and Root Mean Square Values Using a linear voltage amplifier on a feeble signal will result in an output that is a signal at a much higher voltage level, but we cannot necessarily use this signal to operate devices such as a loudspeaker or an electric motor. The reason is that these devices need a substantial amount of current passed through them as well as the voltage across their terminals, and a voltage amplifier cannot supply large currents. What we need is a power amplifier. For example, a voltage amplifier might provide an output that was a voltage wave of 6 V which could supply no more than 1 mA of current. The power amplifier might provide a wave