|
|
PDF NE570 Data sheet ( Hoja de datos )
| Número de pieza | NE570 | |
| Descripción | Telephone trunk comandor | |
| Fabricantes | Philipss | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de NE570 (archivo pdf) en la parte inferior de esta página. Total 12 Páginas | ||
|
No Preview Available !
INTEGRATED CIRCUITS
NE570
Compandor
Product data
Supersedes data of 1990 Jun 07
Philips
Semiconductors
2003 Apr 03
1 page  
Philips Semiconductors
Compandor
Product data
NE570
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 NE570
Compandor, which offers a pair of high performance gain control
circuits featuring low distortion (<0.1 %), high signal-to-noise ratio
(90 dB), and wide dynamic range (110 dB).
CIRCUIT BACKGROUND
The NE570 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 5
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 dB to –80 dB is shown undergoing a 2-to-1 compression where
a 2 dB input level change is compressed into a 1 dB output level
change by the compressor. The original 100 dB of dynamic range is
thus compressed to a 50 dB 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 45 dB.
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
transconductance 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.
INPUT
LEVEL
+20
0 dB
OUTPUT
LEVEL
–20
0 dB
–40
NOISE
–40
–80 –80 SR00679
Figure 5. Restricted dynamic range channel
BASIC CIRCUIT HOOK-UP AND OPERATION
Figure 6 shows the block diagram of one half of the chip, (there are
two identical channels on the IC). The full-wave averaging rectifier
provides a gain control current, IG, for the variable gain (∆G) cell.
The output of the ∆G cell is a current which is fed to the summing
node of the operational amplifier. Resistors are provided to establish
circuit gain and set the output DC bias.
THD_TRIM R3
INV. IN
R2
20 kΩ
∆G_CELL_IN
3, 14
R1
10 kΩ
RECT_IN
2, 15
8, 9 6, 11
5, 12
R3
20 kΩ
∆G –
IG
R4
30 kΩ
VREF
1.8 V
+
1, 16
CRECT
7, 10
OUTPUT
VCC: PIN 13
GND: PIN 4
SR02509
Figure 6. Chip block diagram (1 of 2 channels)
The circuit is intended for use in single power supply systems, so
the internal summing nodes must be biased at some voltage above
ground. An internal band gap voltage reference provides a very
stable, low noise 1.8 V reference denoted VREF. The non-inverting
input of the op amp is tied to VREF, and the summing nodes of the
rectifier and ∆G cell (located at the right of R1 and R2) have the
same potential. The THD_TRIM pin is also at the VREF potential.
Figure 7 shows how the circuit is hooked up to realize an expander.
The input signal, VIN, is applied to the inputs of both the rectifier and
the ∆G cell. When the input signal drops by 6 dB, the gain control
current will drop by a factor of 2, and so the gain will drop 6 dB. The
output level at VOUT will thus drop 12 dB, giving us the desired
2-to-1 expansion.
R3
*CIN1 R2
∆G
–
VIN
*CIN2 R1
R4 VREF +
VOUT
NOTES:
2 R3 VIN (Avg.)
GAIN =
R1 R2 IB
IB = 140 µA
CRECT
* EXTERNAL COMPONENTS
Figure 7. Basic expander
SR02510
2003 Apr 03
5
5 Page 
Philips Semiconductors
Compandor
Product data
NE570
REVISION HISTORY
Rev Date
Description
_3 20030403 Product data (9397 750 11356). ECN 853-2421 29759 of 03 April 2003.
Supersedes data for part-type NE570 included in Product specification NE570/571/SA571 of June 7, 1990.
Modifications:
• Remove all data for part types NE571 and SA571.
19900607 Included in Product specification data sheet NE570/571/SA571. ECN 853-0812 99768.
19861114 Included in Product specification data sheet NE570/571/SA571. ECN 853-0812 86558.
2003 Apr 03
11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet NE570.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| NE570 | Telephone trunk comandor | Philipss |
| NE570 | Compandor |  ON Semiconductor |
| NE570D | Telephone trunk comandor | Philipss |
| NE571 | Compandor | Philipss |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |