High-Pass Filters

Author: J.B. Hoag

Whereas the low-pass filters of the preceding section permitted the passage, more or less, of all frequencies below the cutoff value, and attenuated or suppressed, more or less, all frequencies above this value, high-pass filters do just the reverse. A single L-section high-pass filter is shown in Fig. 7 F and is seen to consist of a series condenser, whose reactance is large for low frequencies and small for higher frequencies, and a shunt inductance, which readily bypasses low frequencies but forces the higher frequencies to continue on out to the load R.

Fig. 7 G. — T- and π-type, high-pass filters

Figure 7 G shows T- and -π-type, one- and two-section high-pass filters which offer greater discrimination to frequencies near the cutoff. The design equations are the same as for the L-section.