LT6600 Linear Technology Corporation, LT6600 Datasheet - Page 9

• Manufacturer Part Number: LT6600
• Description: Very Low Noise, Differential Ampli?er And 2.5mhz Lowpass Filter
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
Interfacing to the LT6600-2.5
Note: The referenced pin numbers correspond to the S8
package. See the Pin Functions for the equivalent DFN-12
package pin numbers.
The LT6600-2.5 requires two equal external resistors, R
to set the differential gain to 1580Ω/R
fi lter are the voltages V
external components, Figure 1. The difference between
V
age of V
Similarly, the voltages V
and 5 of the LT6600-2.5 are the fi lter outputs. The differ-
ence between V
voltage. The average of V
mode output voltage.
Figure 1 illustrates the LT6600-2.5 operating with a single
3.3V supply and unity passband gain; the input signal is
IN
+
and V
IN
+
IN
and V
–
–1
is the differential input voltage. The aver-
2
1
0
OUT
IN
V
3
2
1
0
–
+
3
2
1
0
V
is the common mode input voltage.
and V
500mV
V
OUT
IN
+
OUT
V
P-P
+
and V
IN
OUT
and V
+
(DIFF)
+
and V
V
V
–
V
V
IN
IN
IN
IN
is the differential output
+
+
–
IN
–
OUT
–
t
presented to the see
OUT
t
–
IN
V
appearing at Pins 4
t
IN
. The inputs to the
–
+
V
V
IN
IN
is the common
V
V
0.1μF
0.1μF
–
+
IN
IN
–
+
1580Ω
1580Ω
1580Ω
1580Ω
Figure 1. (S8 Pin Numbers)
Figure 2. (S8 Pin Numbers)
Figure 3. (S8 Pin Numbers)
402Ω
402Ω
0.01μF
0.01μF
0.01μF
–
+
IN
1
7
2
8
1
7
2
8
1
7
2
8
,
2V
LT6600-2.5
LT6600-2.5
LT6600-2.5
–
+
–
+
–
+
3
3
3
6
3.3V
6
3.3V
6
5V
+
+
–
DC coupled. The common mode input voltage is 0.5V, and
the differential input voltage is 2V
output voltage is 1.65V, and the differential output voltage
is 2V
output voltage is determined by the voltage at V
V
mid-supply voltage. In addition, the common mode input
voltage can be equal to the mid-supply voltage of V
Figure 2 shows how to AC couple signals into the LT6600-2.5.
In this instance, the input is a single-ended signal. AC cou-
pling allows the processing of single-ended or differential
signals with arbitrary common mode levels. The 0.1μF
coupling capacitor and the 1580Ω gain setting resistor
form a high pass fi lter, attenuating signals below 1kHz.
Larger values of coupling capacitors will proportionally
reduce this highpass 3dB frequency.
In Figure 3 the LT6600-2.5 is providing 12dB of gain. The
common mode output voltage is set to 2V.
–
+
0.1μF
–
0.1μF
0.1μF
OCM
4
4
4
5
5
5
P-P
is shorted to V
for frequencies below 2.5MHz. The common mode
V
V
V
V
V
V
OUT
OUT
OUT
OUT
OUT
OUT
+
–
+
–
+
–
3
2
1
0
3
2
1
0
3
2
1
0
V
V
V
MID
, the output common mode is the
V
V
V
OUT
OUT
V
V
V
OUT
OUT
OUT
OUT
+
–
660025 F02
+
–
660025 F03
+
–
660025 F01
P-P
t
t
t
LT6600-2.5
. The common mode
OCM
. Since
660025fb
MID
9
.