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參數資料
| 型號： | U4084B |
| 英文描述： | Low-Voltage, Voice-Switched Circuit for Hands-Free Operation |
| 中文描述： | 低電壓，語音開關電路免提操作 |
| 文件頁數： | 13/26頁 |
| 文件大小： | 544K |
| 代理商： | U4084B |
U4084B
Preliminary Information
TELEFUNKEN Semiconductors
Rev. A1, 31-Jan-97
13 (26)
12675
+
–
V
B
2k
Attenuator
control
to attenuators
4
C1 ... C4
Volume control
Dial-tone detector
AGC
12
11
C
T
R
T
C
T
I
1
I
2
60μ
A
Figure 6. C
T
attenuator control block circuit
Operation of the C
T
Circuitry
–
R
T
is typ. 120 k and C
T
is typ. 5.0 F.
–
To switch to receive mode, I
1
is turned on (I
2
is
off), charging the external capacitor to + 240 mV
above V
B.
(An internal clamp prevents further
charging of the capacitor).
–
To switch to transmit mode, I
2
is turned on (I
1
is
off) bringing down the voltage on the capacitor
to – 240 mV with respect to V
B
.
To switch to idle mode quickly (fast idle), the
current sources are turned off, and the internal
2.0-k
resistor is switched on, discharging the
capacitor to V
B
with a time constant = 2.0 k
C
T
.
To switch to idle slowly (slow idle), the current
sources are turned off, the switch at the 2.0-k
resistor is open, and the capacitor discharges to
V
B
with a time constant = R
T
–
–
C
T
.
Microphone Amplifier, Pins 7, 8 and 9
The non-inverting input of the microphone amplifier
(Pins 7 and 8) is connected to V
B
, while the inverting in-
put and the output are pinned out.
Unlike most op amps, the amplifier has an all NPN output
stage which maximizes phase margin and gain band-
width. This feature ensures stability at gains less than
unity, as well with a wide range of reactive loads.
The open loop gain is typically 80 dB (f < 100 Hz), and
the gain-bandwidth is typ. 1.0 MHz (see figure 4). The
maximum p-p output swing is typ. (V
S
– 1 V) with an out-
put impedance of < 10 until current limiting is reached
(typ. 1.5 mA). The input bias current at MIC is typically
– 40 nA.
12676
90k
–
+
9
MUTE
VB
75k
VS
VS
8
MIC
7
MICO
RMF
RMI
from
Mike
Figure 7. Microphone amplifier and mute
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相關代理商/技術參數 |
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| U4084B-FL | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Speakerphone Circuit |
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| U4087B | 制造商:TEMIC 制造商全稱:TEMIC Semiconductors 功能描述:Low Voltage Voice Switch Interface Circuit for Hands-free Operation in Telephone |
| U4087B-FP | 制造商:TEMIC 制造商全稱:TEMIC Semiconductors 功能描述:Low Voltage Voice Switch Interface Circuit for Hands-free Operation in Telephone |
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