Newnes Circuit Calculations Pocket Book

Filters

and

attenuators

319

18.4 High pass filters

High pass filters attenuate

low

frequencies

and

transmit high

frequencies.

The

simple

R-C

filter

is

identical

to the

circuit

in

Figure 18.6,

the

only difference being that

the

output

is

developed

across

the

resistance

as

shown

in

Figure

18.9.

Figure

18.9

A typical frequency response

is

shown

in

Figure

18.10 and the

formula

for

calculating

the

cut-off frequency

is

identical

to

that

in

Section 18.3.

VQUT

Figure

18.10

Figures 18.11

and

18.12 show

T

and

TT

high pass filters respectively.

Both types

are

designed using

the

formulas

Cut-off frequency

f

c

Design impedance

R

Q

4TTV(LC)

•VI

z,z

7

=

320