0

200

0.00

10

190

9.50

25

175

21.88

50

150

37.50

75

125

46.88

100

100

50.00

125

75

46.88

150

50

37.50

175

25

21.88

190

10

9.50

200

0

0.00

6-52. There are components that will vary their impedance (reactance) like the ganged

resistors. As you know, the reactance of an inductor and a capacitor vary as frequency

changes. As frequency increases, inductive reactance increases and capacitive reactance

decreases.

6-53. At some frequency, inductive and capacitive reactance will be equal. That

frequency will depend upon the value of the inductor and capacitor. If the inductor and

capacitor are connected as a parallel LC circuit, you will have the ideal frequency-

determining network for an RF amplifier.

6-54. The parallel LC circuit used as a frequency-determining network is called a tuned

circuit. This circuit is "tuned" to give the proper response at the desired frequency by

selecting the proper values of inductance and capacitance. Figure 6-13 shows a circuit

using this principle. The figure shows an RF amplifier with parallel LC circuits used as

frequency-determining networks. This RF amplifier will only be effective in amplifying

the frequency determined by the parallel LC circuits.

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