Datasheet

Application information TS4990
18/33 Doc ID 9309 Rev 13
4 Application information
4.1 BTL configuration principle
The TS4990 is a monolithic power amplifier with a BTL output type. BTL (bridge tied load)
means that each end of the load is connected to two single-ended output amplifiers. Thus,
we have:
Single-ended output 1 = V
out1
= V
out
(V)
Single-ended output 2 = V
out2
= -V
out
(V)
and V
out1
- V
out2
= 2V
out
(V)
The output power is:
For the same power supply voltage, the output power in BTL configuration is four times
higher than the output power in single-ended configuration.
4.2 Gain in a typical application
The typical application schematics are shown in Figure 1 on page 4.
In the flat region (no C
in
effect), the output voltage of the first stage is (in Volts):
For the second stage: V
out2
= -V
out1
(V)
The differential output voltage is (in Volts):
The differential gain named gain (G
v
) for more convenience is:
V
out2
is in phase with V
in
and V
out1
is phased 180° with V
in
. This means that the positive
terminal of the loudspeaker should be connected to V
out2
and the negative to V
out1
.
4.3 Low and high frequency response
In the low frequency region, C
in
starts to have an effect. C
in
forms with R
in
a high-pass filter
with a -3 dB cut-off frequency. F
CL
is in Hz.
In the high frequency region, you can limit the bandwidth by adding a capacitor (C
feed
) in
parallel with R
feed
. It forms a low-pass filter with a -3 dB cut-off frequency. F
CH
is in Hz.
P
out
2V
out
RMS
()
2
R
L
------------------------------=
V
out1
V–
in
()
R
feed
R
in
--------------
=
V
out2
V
out1
– 2V
in
R
feed
R
in
--------------
=
G
v
V
out2
V
out1
–
V
in
---------------------------------- 2
R
feed
R
in
--------------
==
F
CL
1
2πR
in
C
in
------------------------=
F
CH
1
2πR
feed
C
feed
------------------------------------ -=