Teach Yourself Electricity and Electronics, Sixth Edition, 6th Edition

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CHAPTER

Amplifiers and Oscillators

NOW THAT WE KNOW HOW TRANSISTORS WORK, WE’RE READY TO LEARN ABOUT AMPLIFIERS AND oscillators that use these devices. But first, let’s take a closer look at a topic that we’ve encountered briefly already: the decibel (dB) as an expression of relative signal strength.

The Decibel Revisited

We can consider amplitude increases as positive gain and amplitude decreases as negative gain. For example, if a circuit’s output signal amplitude equals +6 dB relative to the input signal amplitude, then the output exceeds the input. If the output signal amplitude is −14 dB relative to the input, then the output is weaker than the input. In the first case, we say that the circuit has a gain of 6 dB. In the second case, we ...