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参数资料
| 型号： | PBL38814 |
| 厂商： | ERICSSON |
| 英文描述： | Voice - switched 2-channel Circuit with loudspeaker amplifier |
| 中文描述： | 语音-开关2声道扬声器放大器电路 |
| 文件页数： | 10/14页 |
| 文件大小： | 239K |
| 代理商： | PBL38814 |
10
PBL 388 14
Figure 15. External power supply options.
Loudspeaker amplifier
The loudspeaker amplifier drives
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
μ
-processor. See figure 17.
PBL
388 14
21
+
This resistor sets
the max. attenuation
This resistor sets
the min. attenuation
position on the pot.
a).
PBL
388 14
21
+
Weighted
resistors
Three bit
digital
signal
b).
Some optional features using
the dc. set volume control on
the loudspeaker amplifier of
PBL 388 14. ( Fig. 17. )
The DC set volume control has an
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.
a). To control the loudspeaker volume
with a DC- voltage from a potentiometer.
b). To control the loudspeaker volume
with a digital signal ( for ex. 8 - levels ).
c). An AGC can be combined with the
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.
d). A ”softclipping” with a fixed level
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.
e). A ”softclipping” that is controlled by
the ”real” output level that means that the
"softclipping" will follow the changes in the
Figure 17. DC - volume control options.
Figure 16. Loudspeaker volume control. options.
F6
PBL 388 14
12
23
17
21
22
19
AC-control
F6
PBL 388 14
50
LOUD
SPEAKER
+
12
23
17
19
22
21
0V
0V
DC-control
0V
+
+ supply
+ supply
0V
+
50
LOUD
SPEAKER
0V
PBL
388 14
21
To volume
control
Resistor that is added
and which determines
the dynamics of the AGC
10
c).
PBL
388 14
21
To volum
control
Resistor that sets the
"softclipping" level
12
+
+
10
μ
F
pin 4
d).
PBL
388 14
22
To volume
control
21
+
10
μ
F
19
18
Sets the steepness
of the "softclipping"
Resistor that sets the
"softclipping" level
e).
supply voltage and will at all times give the
optimum distortion limiting performance.
+
LSP 19
22
V
A
G 18
A
+
100
16 V
μ
F
0.015 used only
with inductive load
I
+L
GND
17
V
in
Input
23 LSP
in
50
Load
PBL 388 14
1
μ
F
0
μ
VOL 21
V
out
V
A
+
-
I
VOL
LL 20
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相关代理商/技术参数 |
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| PBL388141N | 制造商:ERICSSON 制造商全称:Ericsson 功能描述:Voice - switched 2-channel Circuit with loudspeaker amplifier |
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