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UTC571 参数 Datasheet PDF下载

UTC571图片预览
型号: UTC571
PDF下载: 下载PDF文件 查看货源
内容描述: COMPANDER完整的压缩机和扩张器于一体的Internet控制 [COMPANDER Complete compressor and expandor in one IChip]
分类和应用:
文件页数/大小: 14 页 / 152 K
品牌: UTC [ Unisonic Technologies ]
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UTC571  
LINEAR INTEGRATED CIRCUIT  
INTRODUCTION  
Much interest has been expressed in high performance electronic gain control circuits. For non-critical  
applications, an integrated circuit operational transconductance amplifier can be used, but when high-performance  
is required, one has to resort to complex discrete circuitry with many expensive, well-matched components.  
This paper describes an inexpensive integrated circuit, the UTC571 Compandor, which offers a pair of high  
performance gain control circuits featuring low distortion (<0.1%), high signal-to-noise ratio (90dB), and wide  
dynamic range (110dB).  
CIRCUIT BACKGROUND  
The UTC571 Compandor was originally designed to satisfy the requirements of the telephone system. When  
several telephone channels are multiplexed onto a common line, the resulting signal-to-noise ratio is poor and  
companding is used to allow a wider dynamic range to be passed through the channel. Figure 1 graphically shows  
what a compandor can do for the signal-to-noise ratio of a restricted dynamic range channel. The input level range  
of +20 to -80dB is shown undergoing a 2-to-1 compression where a 2dB input level change is compressed into a  
1dB output level change by the compressor. The original 100dB of dynamic range is thus compressed to a 50dB  
range for transmission through a restricted dynamic range channel. A complementary expansion on the receiving  
end restores the original signal levels and reduces the channel noise by as much as 45dB.  
INPUT  
LEVEL  
+20  
OUTPUT  
LEVEL  
+20  
0d  
B
0dB  
-40  
-80  
-40  
-80  
NOISE  
Figure 1. Restricted Dynamic Range Channel  
The significant circuits in a compressor or expander are the rectifier and the gain control element. The phone  
system requires a simple full-wave averaging rectifier with good accuracy, since the rectifier accuracy determines  
the (input) output level tracking accuracy. The gain cell determines the distortion and noise characteristics, and the  
phone system specifications here are very loose. These specs could have been met with a simple operational  
transconductance multiplier, or OTA, but the gain of an OTA is proportional to temperature and this is very  
undesirable. Therefore, a linearized Tran conductance multiplier was designed which is insensitive to temperature  
and offers low noise and low distortion performance. These features make the circuit useful in audio and data  
systems as well as in telecommunications systems.  
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YOUW ANG ELECTRONICS CO.LTD