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參數(shù)資料
| 型號(hào)： | L3281AB |
| 廠商： | 意法半導(dǎo)體 |
| 英文描述： | LOW VOLTAGE TELEPHONE SPEECH CIRCUITS |
| 中文描述： | 低壓電話語(yǔ)音電路 |
| 文件頁(yè)數(shù)： | 7/10頁(yè) |
| 文件大小： | 170K |
| 代理商： | L3281AB |
ACCHARACTERISTIC
The AC Impedance measured at line terminals is
equalto:
1
jwC1
)
/ /
(
R2
+
R3
+
Zb
)
The value of the capacitor C1 must be In the
rangeof 22
μ
F to 100
μ
F.
The external resistor R1 can be replaced by a re-
sistor/capacitor network in order to realize a com-
plex ImpedanceZm.
Zm
= (
R1
+
TRANSMITTING CIRCUIT
The first block of the TXstage is basically a differ-
ential amplifier which converts voltage to current.
The inputs are internally polarized at 300 mVdc.
The differentialInput impedanceis 60 K
to allow
a good matching to microphone. The AGC in TX
is function of voltage at pin 14 in order to de-
crease to max gain of 5.5dB to 6.0dB when the
linecurrent increases.
RECEIVING CIRCUIT
Fig.9 shows the equivalent receiving circuit. The
differential input of RX signal across R2+R3 is
transferred to the AGC block when the mute sig-
nal (pin10) is not active.
The AGC in RX is a function of the voltage at pin
14 and decreases the gain when the line current
increases(5.5dB to 6.0dB).
The final stage is a single ended amplifier with
low output impedance optimized to drive mag-
netic/dynamictransducers.
Figure8:
Equivalent Transmitting Circuit.
Figure9:
EquivalentReceiving Circuit.
L3281
7/10
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