clc1002 Cadeka Microcircuits LLC., clc1002 Datasheet - Page 13

• Manufacturer Part Number: clc1002
• Description: Ultra-low Noise Amplifer
• Manufacturer: Cadeka Microcircuits LLC.

Data Sheet
Application Information
Basic Operation
Figures 1 and 2 illustrate typical circuit configurations for
non-inverting, inverting, and unity gain topologies for dual
supply applications. They show the recommended bypass
capacitor values and overall closed loop gain equations.
Achieving Low Noise in an Application
Making full use of the low noise of the CLC1002 requires
careful consideration of resistor values. The feedback and
gain set resistors (R
impedance (R
can easily dominate the overall noise if their values are
too high. The datasheet is specified with an R
which point the noise from R
noise from the CLC1002. Lower value resistors could be
used at the expense of more distortion.
Figure 3 shows total input voltage noise (amp+resistors)
versus R
©2007-2008 CADEKA Microcircuits LLC
Input
Input
Figure 1. Typical Non-Inverting Gain Circuit
f
Figure 2. Typical Inverting Gain Circuit
and R
R
R
1
g
source
R
+
-
g
g
+V
-V
. As the value of R
+
-
s
s
) all contribute noise to the circuit and
+V
f
-V
and R
6.8μF
0.1μF
0.1μF
6.8μF
s
s
6.8μF
0.1μF
0.1μF
6.8μF
g
) and the non-inverting source
f
R
and R
f
G = - (R
For optimum input offset
voltage set R
R
f
G = 1 + (R
g
R
f
/R
f
L
is about equal to the
g
increases, the total
Output
)
1
= R
R
f
L
|| R
f
/R
Output
g
g
g
)
of 25Ω, at
input referred noise also increases.
The noise caused by a resistor is modeled with either a
voltage source in series with the resistance:
Or a current source in parallel with it:
Op amp noise is modeled with three noise sources, e
and i
voltage and current errors V
The noise models must be analyzed in-circuit to determine
the effect on the op amp output noise.
Since noise is statistical in nature rather than a continuous
signal, the set of noise sources in circuit add in an RMS
(root mean square) fashion rather than in a linear fashion.
For uncorrelated noise sources, this means you add the
squares of the noise voltages. A typical non-inverting
application (see figure 1) results in the following noise at
the output of the op amp:
op amp noise terms e
e
Figure 3: Input Referred Voltage Noise vs. R
2
o
2.75
2.25
1.75
1.25
0.75
i
2.5
1.5
0.5
. These three sources are analogous to the DC input
= e
3
2
1
100
2
n
1+
R
R
g
f
G = +21
2
+ in
n
, i
i
R
n
2
G = +11
=
4kTR
R
and i
Rf (Ohms)
s
os
2
4kT
, I
R
1+
i
bn
G = +5
R
R
and I
g
f
2
www.cadeka.com
bi
+ i
.
2
i
R
2
f
f
and R
op amp noise terms e
1000
n
g
, i
13
n