R1

C1

-

R2

C2

C

R

R3

C3

-

R4

C4

1st order

2nd order

3rd order

i

i

1/2

TDA2320A

3

2

1

1/2

TDA2320A

5

6

7

Figure 21 : Fifth Order 3.4kHz Low-pass Butterworth Filter

C1

= 1.354 .

1

R

.

1

2

6.33nF

C1

= 0.421 .

1

R

.

1

2

1.97nF

C2

= 1.753 .

1

R

.

1

2

8.20nF

C3

= 0.309 .

1

R

.

1

2

1.45nF

C4

= 3.325 .

1

R

.

1

2

15.14nF

The attenuation of the filter is 30dB at 6.8kHz and

better than 60dB at 15kHz.

Ω, we obtain :

-

10k

Ω

3.54nF

10k

Ω

60nF

-

10k

Ω

16.3nF

10k

Ω

220nF

-

10k

Ω

86.1nF

10k

Ω

161nF

-

0.47

µF

56k

Ω

2

3

1

1/2

TDA

2320A

6

5

7

1/2

TDA

2320A

2

3

1

1/2

TDA

2320A

6

5

7

1/2

TDA

2320A

Figure 22 : Sixth-pole 355Hz Low-pass Filter (Chebychev type)

This is a 6-pole Chebychev type with

±0.25dB ripple

in the passband.A decoupling stage is used to avoid

the influence of the input impedance of the filter’s

characteristics.

The attenuation is about 55dB at 710Hz and

reaches 80dB at 1065Hz. The in band attenuation

is limited in practice to the

±0.25dB ripple and does

TDA2320A

10/12