pbl388141sot ETC-unknow, pbl388141sot Datasheet - Page 10

• Manufacturer Part Number: pbl388141sot
• Description: Voice Switched 2-channel Circuit With Loudspeaker Amplifier
• Manufacturer: ETC-unknow

PBL 388 14
Loudspeaker amplifier
directly a 25 - 50 impedance loudspeaker.
The single ended loudspeaker amplifier
has an internal gain regulation that prevents
distortion in case of insufficient supply
voltage. The loudspeaker volume control
can be solved in two different ways. One is
to use a conventional potentiometer that
will act as an ac voltage divider at the power
amplifier input pin 23. The second is to
control the gain of the power amplifier by
dc. at pin 21. See fig.16. The controlling
element can be a potentiometer or a digital
control from a
the dc. set volume control on
the loudspeaker amplifier of
PBL 388 14. ( Fig. 17. )
wholly internal function to lower the gain at
low supply voltages. This is to avoid that
the power stage dies and causes breaks in
the output signal at low supply currents in
combination with high input signals. This
DC controlled volume is externally
accessible in the PBL 388 14 and can thus
be utilized in several ways.
with a DC- voltage from a potentiometer.
with a digital signal ( for ex. 8 - levels ).
volume control by connecting a resistor
from the DC - control pin 21 to the output of
the receiver detector at pin 10. Care has to
be taken not to disturb the speech switching
balance. If the resistor is made too low
ohmic the same value has to be applied on
the transmitter detector output at pin 6 as
well as that the capacitors at the detector
outputs have to be made bigger.
can be combined with the volume control.
A draw back with the fixed level is that when
setting it in to inhibit clipping distortion at
low supply voltage, the level will not increase
even if the supply voltage would allow it.
the ”real” output level that means that the
"softclipping" will follow the changes in the
10
Some optional features using
The loudspeaker amplifier drives
The DC set volume control has an
a). To control the loudspeaker volume
c). An AGC can be combined with the
d). A ”softclipping” with a fixed level
e). A ”softclipping” that is controlled by
b). To control the loudspeaker volume
-processor. See figure 17.
Figure 17. DC - volume control options.
Figure 15. External power supply options.
Figure 16. Loudspeaker volume control. options.
supply voltage and will at all times give the
optimum distortion limiting performance.
PBL
388 14
PBL
388 14
Input
V
AC-control
b).
a).
in
1 F
19
+
21
21
21
50
SPEAKER
PBL 388 14
23 LSP
0V
LOUD
This resistor sets
the max. attenuation
in
22
F6
+
PBL 388 14
+ supply
+
23
17
12
Weighted
resistors
This resistor sets
the min. attenuation
position on the pot.
GND
17
Three bit
digital
signal
0V
GND
PBL
388 14
LSP 19
VOL 21
PBL
388 14
V
LL 20
d).
A
DC-control
e).
A
PBL
388 14
c).
22
18
19
+
21
12
19
22
18
21
50
SPEAKER
PBL 388 14
0V
21
10
10 F
LOUD
I
VOL
I
+L
21
+
+
+
10 F
+
+
+
0V
0.015 used only
with inductive load
F6
pin 4
100
16 V
22
Resistor that is added
and which determines
the dynamics of the AGC
23
17
12
Resistor that sets the
"softclipping" level
F
+ supply
Sets the steepness
of the "softclipping"
50
Load
Resistor that sets the
"softclipping" level
-
+
V
A
To volum
control
To volume
control
To volume
control
V
0V
out