PBL 388 14
+ supply
+
100 µF
16 V
0 V
50 Ω
LOUDSPEAKER
15nF
19
22
21
20
Tx
signal
23
17
220nF
47k
18
24
4
PBL 388 14
12
50k
100nF
68nF
Control
F3
F6
3
13
11
68nF
68nF
5
+
+
Rx
16
signal
100 µF
6 V
F2
F5
1 µF
150nF
150nF
820Ω
820Ω
15
F4
1
2
+
F1
Ref.
14
9
8
6
10
7
33nF
4.7nF
470 k
6.8nF
MIC.
+
+
+
100 µF
6 V
2.2 µF/6V
100nF
2.2 µF/6V
Figure 18. Application with ac. volume control.
+
22
+
4 - 15 V
-
BD131
PBL
388 14
15n
1000µF
+
19
15n
10Ω
BD132
20
4Ω
The power amplifier feedback loop can
be broken (pinns 19 and 20) thus making it
possble to insert external power transistors
to increase the audio output power. This
enables with external power supply an out-
putpowerofseveralwattsfedinto4-16ohm
loudspeaker. See. fig. 19.
Figure 19. External power amplifier
11
ERICSSON [ ERICSSON ]
