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PDF UTC571 Data sheet ( Hoja de datos )
| Número de pieza | UTC571 | |
| Descripción | Linear Integrated Circuit | |
| Fabricantes | Hangzhou | |
| Logotipo |  |
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UTC571
LINEAR INTEGRATED CIRCUIT
COMPANDER
DESCRIPTION
The UTC571 is a versatile low cost dual gain control
circuit in which either channel may be used as a dynamic
range compressor or expandor. Each channel has a full-
wave rectifier to detect the average value of the signal, a
linerarized temperature-compensated variable gain cell,
and an operational amplifier.
The UTC571 is well suited for use in cellular radio and
radio communications systems, modems, telephone, and
satellite broadcast/receive audio systems.
FEATURES
• Complete compressor and expandor in one IChip
DIP-16
•Temperature compensated
•Greater than 110dB dynamic range
APPLICATIONS
• Operates down to 6VDC
•Cellular radio
• System levels adjustable with external components
•High level limiter
• Distortion may be trimmed out
www.DataSheet4U.com• Dynamic noise reduction systems
•Low level expandor—noise gate
•Dynamic filters
•CD Player
• Voltage-controlled amplifier
PIN CONFIGURATION
RECT CAP 1 1
RECT IN 1 2
AG CELL IN 1 3
GND 4
INV.IN 1 5
RES.R3 1 6
OUTPUT 1 7
THD TRIM 1 8
16 RECT CAP 2
15 RECT IN 2
14 AG CELL IN 2
13 VCC
12 INV.IN 2
11 RES.R 3 2
10 OUTPUT 2
9 THD TRIM 2
YOUW ANG ELECTRONICS CO.LTD
1
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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.
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LEVEL
LEVEL
+20 +20
0dB
0d
B
-40 -40
NOISE
-80
-80
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.
YOUW ANG ELECTRONICS CO.LTD
5
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UTC571
LINEAR INTEGRATED CIRCUIT
4
VOS=5mV
3
4mV
2 3mV
2mV
1
1mV
0.34
-6 0
INPUT LEVEL(dBm)
+6
Figure 10. ∆G Cell Distortion vs Offset Voltage
If the transistors are not perfectly matched, a parabolic, non-linearity is generated, which results in second
harmonic distortion. Figure 10 gives an indication of the magnitude of the distortion caused by a given input level
and offset voltage. The distortion is linearly proportional to the magnitude of the offset and the input level.
Saturation of the gain cell occurs at a +8dBm level. At a nominal operating level of 0dBm, a 1mV offset will yield
0.34% of second harmonic distortion. Most circuits are somewhat better than this, which means our overall offsets
are typically about mV. The distortion is not affected by the magnitude of the gain control current, and it does not
www.DataSheet4U.comincrease as the gain is changed. This second harmonic distortion could be eliminated by making perfect transistors,
but since that would be difficult, we have had to resort to other methods. A trim pin has been provided to allow
trimming of the internal offsets to zero, which effectively eliminated second harmonic distortion. Figure 11 shows
the simple trim network required.
VCC
TO THD
TRIM
6.2K
200PF
R
3.6V
20K
Figure 11. THD Trim Network
YOUW ANG ELECTRONICS CO.LTD
11
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| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet UTC571.PDF ] | |
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