NE570(2003) Ver la hoja de datos (PDF) - Philips Electronics
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NE570 Datasheet PDF : 12 Pages
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Philips Semiconductors
Compandor
Product data
NE570
OPERATIONAL AMPLIFIER
The main op amp shown in the chip block diagram is equivalent to a
741 with a 1 MHz bandwidth. Figure 18 shows the basic circuit. Split
collectors are used in the input pair to reduce gM, so that a small
compensation capacitor of just 10 pF may be used. The output
stage, although capable of output currents in excess of 20 mA, is
biased for a low quiescent current to conserve power. When driving
heavy loads, this leads to a small amount of crossover distortion.
I1
I2
Q6
D1
–IN
Q1 Q2
+IN
D2
OUT
CC
Q5
Q4
Q3
SR02515
Figure 18. Operational amplifier
RESISTORS
Inspection of the gain equations in Figures 7 and 8 will show that the
basic compressor and expander circuit gains may be set entirely by
resistor ratios and the internal voltage reference. Thus, any form of
resistors that match well would suffice for these simple hook-ups,
and absolute accuracy and temperature coefficient would be of no
importance. However, as one starts to modify the gain equation with
external resistors, the internal resistor accuracy and tempco become
very significant. Figure 19 shows the effects of temperature on the
diffused resistors which are normally used in integrated circuits, and
the ion-implanted resistors which are used in this circuit. Over the
critical 0 °C to +70 °C temperature range, there is a 10-to-1
improvement in drift from a 5% change for the diffused resistors, to a
0.5% change for the implemented resistors. The implanted resistors
have another advantage in that they can be made 1/7 the size of the
diffused resistors due to the higher resistivity. This saves a
significant amount of chip area.
1.15
140 Ω /
DIFFUSED RESISTOR
1.10
1 kΩ /
1.05
LOW TC
IMPLANTED RESISTOR
ÇÇÇÇÇÇÇÇÇÇÇÇ 1.00
1% ERROR BAND
0.95
–40
0 40
80 120
TEMPERATURE
SR00693
Figure 19. Resistance versus temperature
2003 Apr 03
9
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