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READING AMPLIFIER FREQUENCYRESPONSE CURVES Figure 22 shows the frequencyresponse curves for four different amplifiers. View (A) is the same frequencyresponse curve as shown in figure 21. View (B) is the frequencyresponse curve of an amplifier that would also be classified as an audio amplifier, even though the curve is not "flat" from 15 hertz to 20 kilohertz and does not drop off sharply at the frequency limits. From the curve, you can see that the lower frequency limit of this amplifier (f_{1}) is 100 hertz. The upper frequency limit (f_{2}) is 10 kilohertz. Therefore, the bandwidth of this amplifier must be 10 kilohertz minus 100 hertz or 9900 hertz. Most amplifiers will have a frequencyresponse curve shaped like view (B) if nothing is done to modify the frequencyresponse characteristics of the circuit. (The factors that affect Frequency response and the methods to modify the Frequency response of an amplifier are covered a little later in this chapter.) Figure 22A.  Frequency response curves.
Figure 22B.  Frequency response curves.
Figure 22C.  Frequency response curves.
Figure 22D.  Frequency response curves.
Now look at view (C). This frequencyresponse curve is for an rf amplifier. The frequency limits of this amplifier are 100 kilohertz (f_{1}) and 1 megahertz (f_{2}); therefore, the bandwidth of this amplifier is 900 kilohertz. View (D) shows another audio amplifier. This time the frequency limits are 30 hertz (f_{1}) and 200 hertz (f_{2}). The bandwidth of this amplifier is only 170 hertz. The important thing to notice in view (D) is that the frequency scale is different from those used in other views. Any frequency scale can be used for a frequencyresponse curve. The scale used would be determined by what frequencies are most useful in presenting the frequencyresponse curve for a particular amplifier. Q.1 What is the bandwidth of an amplifier? 
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