TPA2000D1Q1

2W FILTERLESS MONO CLASSD AUDIO POWER AMPLIFIER

SGLS137B− SEPTEMBER 2002 − REVISED SEPTEMBER 2004

11

POST OFFICE BOX 655303

APPLICATION INFORMATION

C2

C1

L1

L2

OUT−

OUT+

Figure 11. Class-D Output Filter

gain setting via GAIN0 and GAIN1 inputs

The gain of the TPA2000D1 is set by two input terminals, GAIN0 and GAIN1.

The gains listed in Table 1 are realized by changing the taps on the input resistors inside the amplifier. This

by ratios of resistors, so the actual gain distribution from part-to-part is quite good. However, the input

impedance may shift by 30% due to shifts in the actual resistance of the input resistors.

For design purposes, the input network (discussed in the next section) should be designed assuming an input

impedance of 20 k

Ω, which is the absolute minimum input impedance of the TPA2000D1. At the higher gain

settings, the input impedance could increase as high as 115 k

Ω.

Table 2. Gain Settings

GAIN0

GAIN1

AMPLIFIER GAIN

(dB)

INPUT IMPEDANCE

(k

Ω)

GAIN0

GAIN1

TYP

TYP

0

0

6

104

0

1

12

74

1

0

18

44

1

1

23.5

24

input resistance

Each gain setting is achieved by varying the input resistance of the amplifier, which can range from its smallest

value to over six times that value. As a result, if a single capacitor is used in the input high-pass filter, the −3 dB

or cutoff frequency also changes by over six times.

Ci

IN

Zi

Zf

Input

Signal