Earlier chapters discussed amplifiers operating in their normal
frequency range. Now, we want to discuss how an amplifier responds
when the input frequency is outside this normal range. With ac
amplifiers, the voltage gain decreases when the input frequency is too
low or too high. On the other hand, dc amplifiers have voltage gain all
the way down to zero frequency. It is only at higher frequencies that
the voltage gain of a dc amplifier falls off. We can use decibels to
describe the decrease in voltage gain and a Bode plot to graph the
response of an amplifier.
