Philips Semiconductors

TDA8945S

15 W mono BTL audio amplifier

Product specification

Rev. 02 — 7 April 2000

4 of 21

9397 750 06866

© Philips Electronics N.V. 2000. All rights reserved.

8.1 Input configuration

The TDA8945S inputs can be driven symmetrical (floating) as well as asymmetrical.

In the asymmetrical mode one input pin is connected via a capacitor to the signal

ground which should be as close as possible to the SVR (electrolytic) capacitor

coupling capacitors for both pins are necessary.

The input cut-off frequency is:

(1)

(2)

As shown in Equation 1 and 2, large capacitor values for the inputs are not

minimized. This results in a good low frequency response and good switch-on

behaviour.

Remark: To prevent HF oscillations do not leave the inputs open, connect a capacitor

of at least 1.5 nF across the input pins close to the device.

8.2 Power amplifier

The power amplifier is a Bridge Tied Load (BTL) amplifier with an all-NPN output

stage, capable of delivering a peak output current of 2 A.

The BTL principle offers the following advantages:

8.2.1

Output power measurement

The output power as a function of the supply voltage is measured on the output pins

at THD = 10%; see Figure 8. The maximum output power is limited by the maximum

supply voltage of 18 V and the maximum available output current: 2 A repetitive peak

current.

f

i cut

off

–

()

1

2

π R

i

C

i

×

()

-----------------------------

=

f

i cut

off

–

()

1

2

π 45 10

3

×

220

×

10

9

–

×

()

-----------------------------------------------------------------

16 Hz

==