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| 型號： | U4090B-P |
| 英文描述： | Low power dual voltage comparators |
| 中文描述： | U4090B磷[更新9 / 03。 34頁] |
| 文件頁數(shù)： | 10/34頁 |
| 文件大小： | 622K |
| 代理商： | U4090B-P |
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10
U4090B-N
4740A–CORD–09/03
A detailed diagram of the AFS (acoustic feedback suppression) is given in Figure 9.
Receive and transmit signals are first processed by logarithmic rectifiers in order to pro-
duce the envelopes of the speech at TLDT and RLDT. After amplification, a decision is
made by the differential pair which direction should be transmitted.
The attenuation of the controlled amplifiers TXA and SAI is determined by the emitter
current IAT which consists of three parts:
I
AT
= I
ATAFS
- I
ATGSA
- I
AGAFS
G = I
AT
0.67 dB/μA
Figure 10 illustrates the principle relationship between speaker amplifier gain (GSA) and
attenuation of AFS (ATAFS). Both parameters can be adjusted independently, but the
internal coupling between them has to be considered. The maximum usable value of
GSA is 36 dB. The shape of the characteristic is moved in the x-direction by adjusting
resistor RATAFS, thus changing ATAFS
m
. The actual value of attenuation (ATAFS
a
),
however, can be determined by reading the value which belongs to the actual gain
GSA
a
. If the speaker amplifier gain is reduced, the attenuation of AFS is automatically
reduced by the same amount in order to achieve a constant loop gain. Zero attenuation
is set for speaker gains
GSA GSA0 = 36 dB - ATAFS
m
.
Figure 10.
Reducing Speaker Amplifier Gain Results in an Equal Reduction of AFS
Attenuation
I
ATAS
I
ATGSA
I
AGAFS
sets maximum attenuation
decreases the attenuation when speaker amplifier gain is reduced
decreases the attenuation according to the loop gain reduction caused
by the AGA function
ATAFS (dB)
36 dB
ATAFS
m
ATAFS
a
GSA
o
GSA
a
GSA (dB)
not usable
RATAFS
RATAFS
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|---|---|
| U4090B-PFNG3Y | 功能描述:電信語音調(diào)制 IC COM.CORDED - FEATURE RoHS:否 制造商:Epson Electronics America 產(chǎn)品: 應(yīng)用:Voice Guidance product 封裝 / 箱體:PQFP-52 電源電壓-最大:3.6 V, 5.5 V 最大工作溫度: 最小工作溫度: 封裝: |
| U4090B-PFNY | 功能描述:電信語音調(diào)制 IC COM.CORDED - FEATURE RoHS:否 制造商:Epson Electronics America 產(chǎn)品: 應(yīng)用:Voice Guidance product 封裝 / 箱體:PQFP-52 電源電壓-最大:3.6 V, 5.5 V 最大工作溫度: 最小工作溫度: 封裝: |
| U4091B | 制造商:TEMIC 制造商全稱:TEMIC Semiconductors 功能描述:Programmable Telephone Audio Processor |
| U4091BM | 制造商:TEMIC 制造商全稱:TEMIC Semiconductors 功能描述:Programmable Telephone Audio Processor |
| U4091BM-AFN | 制造商:TEMIC 制造商全稱:TEMIC Semiconductors 功能描述:Programmable Telephone Audio Processor |
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