MM0704, Lesson 2
T-section. Tank circuits (figure 2-10), connected in series, improve the filtering action by reducing the opposition to
the desired frequency. Thus, L1-C1 and L2-C2 work together to deliver current to the load between f1 and f2, while L3
and C3 short to ground those currents above and below the cutoff frequencies.
Figure 2-10. T-Section, Band-Pass Filter
-section. Inductor L1 and capacitor C1 are selected to transmit freely between f1 and f2 (frequencies) and permit the
desired frequency currents to reach the output (figure 2-11). The parallel circuits shunting the load are tuned to either
side of f1 and f2 to provide an easy path to ground for all other frequencies. The designer of this circuit has the option
of tuning L2-C2 below f1 and L3-C3 above f2, or vice versa.
Figure 2- 11. -Section, Band-Pass Filter.