LT6604-15 Linear Technology, LT6604-15 Datasheet - Page 10

• Manufacturer Part Number: LT6604-15
• Description: Dual Very Low Noise Differential Amplifier and 15MHz Lowpass Filter
• Manufacturer: Linear Technology

APPLICATIONS INFORMATION
LT6604-15
In Figure 3 the LT6604-15 is providing 12dB of gain. The
gain resistor has an optional 62pF in parallel to improve
the passband fl atness near 15MHz. The common mode
output voltage is set to 2V.
Use Figure 4 to determine the interface between the
LT6604-15 and a current output DAC. The gain, or “tran-
simpedance,” is defi ned as A = V
transimpedance, use the following equation:
By setting R1 + R2 = 536Ω, the gain equation reduces
to A = R1 (Ω).
The voltage at the pins of the DAC is determined by R1,
R2, the voltage on V
Consider Figure 4 with R1 = 49.9Ω and R2 = 487Ω. The
10
A =
V
(R1+R2)
CURRENT
536 • R1
OUT
OUTPUT
I
IN
DAC
+
+
– V
– I
IN
OUT
–
I
I
–
IN
IN
(Ω)
–
+
=
536 • R1
R1 + R2
R1
R1
3
2
1
0
MID
V
0.01μF
500mV
R2
R2
Figure 4
and the DAC output current.
P-P
(DIFF)
34
OUT
4
6
2
V
V
–
1/2
+
IN
IN
LT6604-15
25
3.3V
7
+
–
/I
IN
+
–
0.1μF
. To compute the
27
29
t
V
V
IN
IN
660415 F04
–
+
V
V
OUT
OUT
+
–
62pF
133Ω
62pF
133Ω
0.01μF
Figure 3
+
–
voltage at V
DAC pins is given by:
I
49.8Ω.
Evaluating the LT6604-15
The low impedance levels and high frequency operation
of the LT6604-15 require some attention to the matching
networks between the LT6604-15 and other devices. The
previous examples assume an ideal (0Ω) source impedance
and a large (1k) load resistance. Among practical examples
2V
IN
34
NETWORK
ANALYZER
SOURCE
4
6
2
V
= 77mV +I
is I
1/2
–
LT6604-15
+
DAC
50Ω
25
7
5V
IN
+
–
+
0.1μF
= V
27
29
or I
MID
MID
52.3Ω
IN
IN
COILCRAFT
TTWB-1010
, for V
V
V
–
•
OUT
OUT
• 45.3Ω
. The transimpedance in this example is
1:1
R1+R2+ 536
+
–
523Ω
523Ω
S
3
2
1
0
= 3.3V, is 1.65V. The voltage at the
R1
V
34
4
6
2
Figure 5
1/2
LT6604-15
+
–
25
–2.5V
7
2.5V
+
–
0.1μF
0.1μF
+I
27
29
V
V
www.DataSheet4U.com
OUT
IN
OUT
+
–
•
660415 F03
402Ω
402Ω
R1+R2
R1• R2
COILCRAFT
TTWB-16A
t
4:1
NETWORK
ANALYZER
INPUT
660415fa
660415 F05
50Ω