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PBL3852 参数 Datasheet PDF下载

PBL3852图片预览
型号: PBL3852
PDF下载: 下载PDF文件 查看货源
内容描述: 通用传输电路 [Universal Transmission Circuit]
分类和应用:
文件页数/大小: 24 页 / 407 K
品牌: ERICSSON [ ERICSSON ]
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PBL 3852  
mum signal amplitude that can be  
transmitted to the line undistorted is  
dependent of R7.(amplitude limiting) The  
figure 20 shows the range for the  
amplitude limiter dependent of the  
operating point on the DC characteristic.  
The transmitter gain and frequency  
response are set by the RC-network  
between the pins MO and TI (See fig. 11). the transmitter has an unacceptable low  
The capacitor for cutting the high sving to the line at low line currents  
frequency end is best to be placed directly <10mA the first should be to examine if  
at the microphone where it will also act as the circuits DC- characteristic can be  
a RFI suppressor. The input signal source adjusted upwards and first secondly make  
impedance to the transmitter amplifier  
input TI should be reasonably low in order  
to keep the gain spread down, saying that  
R4//R5//R6 (see fig. 32) must be at least a  
factor of 5 lower than the ZTin. Observe  
that the capacitor C9 should have a  
reasonably good temperature behaviour  
in order to keep the impedance rather  
constant. The V+C´s influence on the  
transmitter DC-characteristic is shown in  
the fig. 8 therefore the transmitter gain  
would change if the transmitted signal  
gives reason to an ac-voltage leak signal  
across C9, this being a feedback point. If  
Transmitter amplifier  
The transmitter amplifier in PBL 3852  
consists of three stages. The first stage is  
an amplitude limiter for the input signal at  
TI, in order to prevent the transmitted  
signal to exceed a certain set level and  
cause distortion. The second stage  
amplifies further the signal from the first  
and adds it to a DC level from an internal  
DC-regulation loop in order to give the  
required DC characteristic to the  
telephone set. The output for this stage is  
TO. The third stage is a current generator  
that presents a high impedance towards  
the line and has its gain from TO to +L.  
The gain of this amplifier is ZL/R7 where  
ZL is the impedance across the tele-  
phone line. Hence, the absolute maxi-  
use of the linear PD.  
11  
3
3
11  
3
11  
(b)  
CA  
(c)  
(a)  
RA  
RA  
CA  
RA  
CA  
(a),(c), (d)  
RB  
no attn.  
CB  
attenuation  
no attn.  
(b),(e)  
3
11  
11  
(e)  
11  
3
3
(d)  
CA  
(f)  
CC  
RA  
CC  
RA  
RA  
CA  
CA  
big C  
A
small C  
A
RB  
CB  
RB  
RB  
CB  
(f)  
attn.without dc.  
attenuation  
attn.without dc.  
Figure 11. Different possible types of networks between microphone amplifier and transmitter.  
Receiver amplifier  
amplifier uses at max. swing (4-6) mA  
peak. This current is drawn from DC2  
that can supply 2 mA continuous  
current, the C3 helping to supply the  
peaks, this applies for speech signals  
only. Continuous sinusoidal signals at  
this level will load the DC2 down. If a  
distortion appears in the earphone  
amplifier output at high signal levels,  
high line currents, low ohmic earphone  
load or at low frequencies, the most  
probable fault is that the filtering  
regulated differential amplifier and the  
third stage a balanced power amplifier.  
The power amplifier has a differential  
output that does not need a series  
capacitor with the load. The receiver  
The receiver amplifier consists of three  
stages, the first stage being an input  
buffer that renders the input a high  
impedance. The second stage is a gain  
(d)  
(b)  
(c)  
(a)  
17  
17  
17  
150Ω  
150Ω  
-
-
-
Z
+
+
+
Rx  
Rx  
Rx  
+
+
+
+
16  
16  
16  
capacitor of the earphone amplifier  
supply C3 is too small. At low line  
currents (normal case, I < 10 mA)  
L
Figure 12. Receiver arrangements.  
8