PBL3853SO 查看數據表（PDF） - Ericsson
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PBL3853SO Datasheet PDF : 16 Pages
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PBL 3853
Detailed Description: Expressions for AC-characteristics
ZLine is the impedance that the telephone sees in the telephone line. Zp is the impedance formed by the passive
(see fig,15.) elements in the telephone set. R1, R2 and C2 . 1/Zp = 1/R1+2πf C2 (R2 can be omitted if R2 << R1)
Active impedance:
The following expression is derived from fig.12 if 1/ZLoad = 1/Zp + 1/Zline
+ = −
VY
R5
1+
R
R
12
13
ZLoad
γ
δVS α
VY
................................................................................................................1
Figure 12 and the expression above render the following transmitter gain expression:
Transmitter
gain = VL = VY
VS VS
−1(1+ R 12 / R 13)
R5
ZLoad
=
− α δ (1+ R 12 / R 13) ZLoad
( ) R 5 + 1+ R 12 / R 13 ZLoad α γ
...........................................................2
Figure 12 renders the following expression of the impedance across the circuit:
Impedance across the circuit
=
VL
ILoad
=
1
...............................................................3
( ) 1/ ZLoad + 1+ R12 / R13 ZLoad α γ / R5
Figure 12 renders also the following expression of the impedance across R5:
( ) Impedance across R5 =
VY
I1
=
1/ R 5 +1/
1
(1+ R 12 / R 13) ZLoad α γ
.............................................................................4
From figure 13 it is possible to identify δ: δ = A1 R4 / /15000 10 ............................................................................5
R4 / /15000 + R3 15
From figure 13 it is possible to identify α: α = 5.8
From figure 13 it is possible to identify γ:
γ = 0.7 R2 / /8000
R2 / /8000 + R1
1+
10000
15000 + R3
/
/R4
...............................................................................................................6
These expressions together by omitting the impedance of the
line ZLine from the expression, will render the impedance of thetelephone
set towards the line.The telephone set impedance towards the line is:
VL
ILoad
=
1
+
R1 + 2ΠfC2
0.7 R2 / /8000
R2 / /8000 + R1
1
5. 8
R5
1+
10000
15000 + R3
/
/R4
1+
R12
R13
..............................................................................7
Zactive
Telephone
Iload
Zp
Telephone line
IL
Zline
Figure 12 .
8
Zload
PBL 3853
2
15
R7
C7
VL
R5 R10
C*
Figure 13.
R11
Z bal
* To give receiver flat
frequency response
+Line
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