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

• Manufacturer Part Number: LT6604-10
• Description: Dual Very Low Noise, Differential Ampli?er And 10mhz Lowpass Filter
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
LT6604-10
In Figure 3 the LT6604-10 is providing 12dB of gain. The
gain resistor has an optional 62pF in parallel to improve
the passband fl atness near 10MHz. The common mode
output voltage is set to 2V.
Use Figure 4 to determine the interface between the
LT6604-10 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 = 402Ω, 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
I
10
IN
–
A =
). Consider Figure 4 with R1 = 49.9Ω and R2 = 348Ω.
(R1+R2)
402 • R1
(Ω)
MID
and the DAC output current (I
3
2
1
0
V
500mV
P-P
(DIFF)
OUT
V
V
IN
IN
V
+
–
/I
CURRENT
OUT
OUTPUT
I
IN
IN
DAC
+
+
. To compute the
– V
– I
t
IN
OUT
–
V
V
I
I
–
IN
IN
IN
IN
–
+
–
+
=
402 • R1
R1 + R2
R1
R1
IN
62pF
100Ω
62pF
100Ω
+
0.01μF
or
0.01μF
R2
R2
Figure 4
Figure 3
+
–
The voltage at V
the DAC pins is given by:
I
50.4Ω.
Evaluating the LT6604-10
The low impedance levels and high frequency operation
of the LT6604-10 require some attention to the matching
networks between the LT6604-10 and other devices. The
previous examples assume an ideal (0Ω) source impedance
and a large (1k) load resistance. Among practical examples
where impedance must be considered is the evaluation of
the LT6604-10 with a network analyzer.
2V
IN
34
34
4
6
2
4
6
2
=103mV +I
is I
V
1/2
1/2
+
LT6604-10
–
LT6604-10
–
+
DAC
25
25
7
3.3V
7
5V
IN
+
–
+
–
0.1μF
+
0.1μF
= V
27
27
29
29
or I
MID
IN
660410 F04
IN
V
V
–
V
V
MID
OUT
OUT
•
. The transimpedance in this example is
OUT
OUT
R1+R2+ 402
• 43.6Ω
+
–
+
–
, for V
3
2
1
0
R1
V
S
= 3.3V, is 1.65V. The voltage at
+I
V
V
OUT
OUT
IN
+
–
•
660410 F03
R1+R2
R1• R2
t
660410fb