OP471 Datasheet, PDF (8/16 Pages) Analog Devices – High Speed, Low Noise Quad Operational Amplifier

OP471
1000
OP11
OP400
OP471
100
OP470
RESISTOR
NOISE ONLY
10
100
1k
10k
RS – SOURCE RESISTANCE – ⍀
100k
Figure 6. Peak-to-Peak Noise (0.1 Hz to 10 Hz) vs. Source
Resistance (Includes Resistor Noise)
Figure 6 shows peak-to-peak noise versus source resistance over
the 0.1 Hz to 10 Hz range. Once again, at low values of R_S, the
voltage noise of the OP471 is the major contributor to peak-to-peak
noise. Current noise becomes the major contributor as R_S increases.
The crossover point between the OP471 and the OP400 for
peak-to-peak noise is at R_S = 17 W.
The OP470 is a lower noise version of the OP471, with a typical
noise voltage density of 3.2 nV/÷Hz @ 1 kHz. The OP470 offers
lower offset voltage and higher gain than the OP471, but is a slower
speed device, with a slew rate of 2 V/ms compared to a slew rate
of 8 V/ms for the OP471.
For reference, typical source resistances of some signal sources
are listed in Table I.
Device
TABLE I.
Source
Impedance Comments
Strain gauge < 500 W
Typically used in
low-frequency applications.
Magnetic
tapehead
< 1,500 W
Magnetic
phonograph
cartridges
< 1,500 W
Low I_B very important to reduce
self-magnetization problems
when direct coupling is used.
OP471 I_B can be neglected.
Similar need for low I_B in direct
coupled applications. OP471
will not introduce any
self -magnetization problem.
Linear variable < 1,500 W
differential
transformer
Used in rugged servo-feedback
applications. Bandwidth of
interest is 400 Hz to 5 kHz.
*For further information regarding noise calculations, see “Minimization of
Noise in Op Amp Applications,” Application Note AN-15.
R3
1.24k⍀
R1
5⍀
R2
5⍀
OP471
DUT
C1
2␮F
OP27E
C4
R5
909⍀
R6
600k⍀
0.22␮F
R10
R11
R4
200⍀
D1
1N4148
D2
1N4148
OP15E
R9
65.4k⍀
65.4k⍀
C3
0.22␮F
OP15E
R14
4.99k⍀
e_OUT
306k⍀
C5
R13
1␮F
5.9k⍀
R8
10k⍀
C2
0.032␮F
R12
10k⍀
GAIN = 50,000
V_S = ؎15V
Figure 7. Peak-to-Peak Voltage Noise Test Circuit (0.1 Hz to 10 Hz)
–8–
REV. A