20W/40W, Filterless, Spread-Spectrum,

Mono/Stereo, Class D Amplifier

18

______________________________________________________________________________________

Figure 6. Fully Differential Crossover Filters

BIAS

2

3

1

C1

47nF

R3

28k

Ω

R2, 56.2k

Ω

R1

56.2k

Ω

C2

47nF

MAX4478

U1A

BIAS

6

5

7

C3

47nF

R7

28k

Ω

R6, 56.2k

Ω

RIGHT

AUDIO

OUTPUT

RIGHT

AUDIO

INPUT

R5

56.2k

Ω

R4

28k

Ω

C4

47nF

MAX4478

U1B

BIAS

9

10

8

C5

47nF

R10

28k

Ω

R9, 56.2k

Ω

R8

56.2k

Ω

C6

47nF

MAX4478

U1C

BIAS

13

12

14

C7

47nF

R14

28k

Ω

R13, 56.2k

Ω

LEFT

AUDIO

OUTPUT

SUBWOOFER OUTPUT IS

AC-COUPLED TO A

MAX9708 CONFIGURED AS

A MONO AMPLIFIER

NOTE:

OP-AMP POWER PINS OMITTED FOR CLARITY.

ALL RESISTORS ARE 1% OR BETTER.

ALL CAPACITORS ARE 5% OR BETTER.

RIGHT AND LEFT OUTPUTS

ARE AC-COUPLED TO A

MAX9708 CONFIGURED AS

A STEREO AMPLIFIER

SUBWOOFER

AUDIO

OUTPUT

LEFT

AUDIO

INPUT

R12

56.2k

Ω

R11

28k

Ω

C8

47nF

MAX4478

U1D

BIAS

2

3

1

R17

26.1k

Ω

R15

26.1k

Ω

MAX4478

U2A

R16

13k

Ω

C9, 47nF

C10

47nF

R18

7.5k

Ω

BIAS

6

5

7

R21

28k

Ω

R19

26.1k

Ω

MAX4478

U2B

R20

13k

Ω

C11, 47nF

R22

7.5k

Ω