Datasheet

MAX410/MAX412/MAX414
circuit shown in Figure 3. Figure 4 shows the frequency
response of the circuit. The test time for the 0.1Hz to
10Hz noise measurement should be limited to 10 sec-
onds, which has the effect of adding a second zero to
the test circuit, providing increased attenuation for fre-
quencies below 0.1Hz.
Current Noise Testing
The current-noise density can be calculated, once the
value of the input-referred noise is determined, by
using the standard expression given below:
where:
R
n
= Inverting input effective series resistance
R
p
= Noninverting input effective series resistance
e
no
= Output voltage-noise density at the frequency of
interest (V/√Hz)
i
n
= Input current-noise density at the frequency of
interest (A/√Hz)
A
VCL
= Closed-loop gain
T = Ambient temperature in Kelvin (K)
k = 1.38 x 10
-23
J/K (Boltzman’s constant)
R
p
and R
n
include the resistances of the input driving
source(s), if any.
If the Quan Tech model 5173 is used, then the A
VCL
terms in the numerator and denominator of the equation
given above should be eliminated because the Quan
i
e
AHz
n
no VCL n p
n p VCL
2
2
- (A ) (4kT)(R +R )
(R +R )(A )
=
[]
/
Figure 3. 0.1Hz to 10Hz Voltage Noise Test Circuit
10Ω D.U.T
MAX410
0.1µF
100kΩ
+V
S
-V
S
2kΩ
4.7µF
+V
S
-V
S
100kΩ
0.1µF
24.9kΩ
2kΩ
4.7µF
22µF
TO SCOPE x1
R
IN
= 1MΩ
110kΩ
MAX410
MAX412
MAX414
Figure 4. 0.1Hz to 10Hz Voltage Noise Test Circuit, Frequency
Response
FREQUENCY (Hz)
GAIN (dB)
1010.1
20
40
60
80
100
0
0.01 100
Single/Dual/Quad, 28MHz, Low-Noise,
Low-Voltage, Precision Op Amps
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