SA571
Figure 15 shows the noise performance of the
DG
cell.
The maximum output level before clipping occurs in the
gain cell is plotted along with the output noise in a 20 kHz
bandwidth. Note that the noise drops as the gain is reduced
for the first 20 dB of gain reduction. At high gains, the signal
to noise ratio is 90 dB, and the total dynamic range from
maximum signal to minimum noise is 110 dB.
+20
0
OUTPUT (dBm)
−20
−40
−60
−80
NOISE IN
20kHz BW
−100
−40
−20
0
VCA GAIN (0dB)
110dB
MAXIMUM
SIGNAL LEVEL
90dB
V
CC
R−SELECT FOR
3.6V
100kW
470kW
TO PIN 3 OR 14
Figure 16. Control Signal Feedthrough
Operation Amplifier
The main op amp shown in the chip block diagram is
equivalent to a 741 with a 1.0 MHz bandwidth. Figure 17
shows the basic circuit. Split collectors are used in the input
pair to reduce g
M
, 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.
I
1
I
2
Q
6
−IN
+IN
Figure 15. Dynamic Range
Control signal feedthrough is generated in the gain cell by
imperfect device matching and mismatches in the current
sources, I
1
and I
2
. When no input signal is present, changing
I
G
will cause a small output signal. The distortion trim is
effective in nulling out any control signal feedthrough, but
in general, the null for minimum feedthrough will be
different than the null in distortion. The control signal
feedthrough can be trimmed independently of distortion by
tying a current source to the
DG
input pin. This effectively
trims I
1
. Figure 16 shows such a trim network.
Q
1
Q
2
C
C
D
1
D
2
Q
2
OUT
Q
3
Q
4
Figure 17. Operational Amplifier
ORDERING INFORMATION
Device
SA571D
SA571DG
SA571DR2
SA571DR2G
SA571N
SA571NG
Description
16−Pin Plastic Small Outline (SO−16 WB) Package
16−Pin Plastic Small Outline (SO−16 WB) Package
(Pb−Free)
16−Pin Plastic Small Outline (SO−16 WB) Package
16−Pin Plastic Small Outline (SO−16 WB) Package
(Pb−Free)
16−Pin Plastic Dual In−Line Package (PDIP−16)
16−Pin Plastic Dual In−Line Package (PDIP−16)
(Pb−Free)
Temperature Range
−40 to +85°C
−40 to +85°C
−40 to +85°C
−40 to +85°C
−40 to +85°C
−40 to +85°C
Shipping
†
47 Units / Rail
47 Units / Rail
1000 / Tape & Reel
1000 / Tape & Reel
25 Units / Rail
25 Units / Rail
†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging
Specifications Brochure, BRD8011/D.
http://onsemi.com
9
ONSEMI [ ON SEMICONDUCTOR ]
