LTC6404 Linear Technology, LTC6404 Datasheet - Page 24
LTC6404
Manufacturer Part Number
LTC6404
Description
High Precision Fully Differential Input/Output Amplifier/Driver
Manufacturer
Linear Technology
Datasheet
1.LTC6404.pdf
(28 pages)
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APPLICATIONS INFORMATION
LTC6404
capacitor solution of 12pF from each fi ltered output to
ground plus a 12pF capacitor between the fi ltered outputs
would also halve the fi lter bandwidth (Figure 8).
24
Figure 8. LTC6404 Filter Topology Modifi ed for 1/2x Filter
Bandwidth (3 External Capacitors)
LTC6404
+
–
14
7
OUT
OUT
50Ω
50Ω
–
+
13
8
12pF
12pF
OUTF
OUTF
12pF
e
–
+
ncm
V
V
–
–
6404 F08
2
V
V
V
V
–
–
+
–
12
9
12pF
1
2
3
4
SHDN
V
V
V
e
e
12pF
12pF
+
–
OCM
nRI2
nRI1
FILTERED OUTPUT
(44.25MHz)
16
V
V
5
SHDN
+
–
2
2
Figure 9. Noise Model of the LTC6404
i
i
NC
NC
n
n
e
R
R
+2
–2
ni
I2
I1
2
15
6
IN
IN
R
R
+
–
V
+
–
F2
F1
OCM
e
e
nRF2
nRF1
14
7
2
2
OUT
OUT
Noise Considerations
The LTC6404’s input referred voltage noise is on the
order of 1.5nV/√Hz. Its input referred current noise is on
the order of 3pA/√Hz. In addition to the noise generated
by the amplifi er, the surrounding feedback resistors also
contribute noise. A noise model is shown in Figure 9.
The output noise generated by both the amplifi er and the
feedback components is governed by the equation:
A plot of this equation, and a plot of the noise generated
by the feedback components for the LTC6404 is shown
in Figure 10.
–
+
13
e
8
no
OUTF
OUTF
V
=
+
LTC6404
–
+
V
V
–
–
6404 F09
⎛
⎜
⎝
2
V
V
V
V
e
–
+
+
–
•
12
11
10
9
ni
⎛
⎜
⎝
e
•
n
⎛
⎝ ⎜
R R I
1
+
V
V
V
•
–
+
–
⎛
⎝ ⎜
R
R
R
R
F
I
e
F
I
⎞
⎠ ⎟
nof
⎞
⎠ ⎟
⎞
⎟ +
⎠
2
⎞
⎟ +
⎠
2
2
e
2
no
2
2
•
(
•
I R
e
n
nRF
•
2
F
)
2
+
6404f