LT6600-20 Linear Technology, LT6600-20 Datasheet - Page 7

• Manufacturer Part Number: LT6600-20
• Description: Very Low Noise Differential Amplifier and 20MHz Lowpass Filter
• Manufacturer: Linear Technology

APPLICATIO S I FOR ATIO
Interfacing to the LT6600-20
The LT6600-20 requires two equal external resistors, R
to set the differential gain to 402 /R
filter are the voltages V
external components, Figure 1. The difference between
V
of V
Similarly, the voltages V
4 and 5 of the LT6600-20 are the filter outputs. The
difference between V
output voltage. The average of V
common mode output voltage.
Figure 1 illustrates the LT6600-20 operating with a single
3.3V supply and unity passband gain; the input signal is
DC coupled. The common mode input voltage is 0.5V, and
the differential input voltage is 2V
IN
+
IN
and V
+
and V
IN
–
is the differential input voltage. The average
IN
–
–1
2
1
0
3
2
1
0
3
2
1
0
is the common mode input voltage.
U
V
V
V
OUT
500mV
V
V
OUT
IN
IN
IN
+
+
–
U
+
P-P
+
and V
V
and V
(DIFF)
IN
and V
V
+
V
IN
IN
+
–
P-P
OUT
IN
OUT
OUT
W
–
. The common mode
IN
–
t
presented to these
t
+
–
t
. The inputs to the
is the differential
appearing at Pins
and V
V
V
V
V
V
IN
IN
IN
IN
IN
–
+
–
+
+
OUT
0.1 F
0.1 F
402
402
U
62pF
100
62pF
100
–
0.01 F
402
402
is the
0.01 F
0.01 F
IN
Figure 1
Figure 2
Figure 3
+
–
,
1
7
2
8
1
7
2
8
LT6600-20
+
2V
–
3
3.3V
6
–
LT6600-20
+
1
7
2
8
3
6
output voltage is 1.65V, and the differential output voltage
is 2V
output voltage is determined by the voltage at pin 2. Since
pin 2 is shorted to pin 7, the output common mode is the
mid-supply voltage. In addition, the common mode input
voltage can be equal to the mid-supply voltage of Pin 7
(see the Distortion vs Input Common Mode Level graphs
in the Typical Performance Characteristics).
Figure 2 shows how to AC couple signals into the
LT6600-20. In this instance, the input is a single-ended
signal. AC coupling allows the processing of single-ended
or differential signals with arbitrary common mode levels.
The 0.1 F coupling capacitor and the 402 gain setting
resistor form a high pass filter, attenuating signals below
4kHz. Larger values of coupling capacitors will propor-
tionally reduce this highpass 3dB frequency.
5V
+
–
0.1 F
–
LT6600-20
+
+
–
0.1 F
4
5
3.3V
3
6
4
5
P-P
+
–
0.1 F
4
5
for frequencies below 20MHz. The common mode
V
V
OUT
OUT
V
V
OUT
OUT
+
–
V
V
+
–
OUT
OUT
+
–
3
2
1
0
3
2
1
0
V
V
3
2
1
0
V
V
V
V
V
OUT
OUT
OUT
OUT
+
V
V
–
www.DataSheet4U.com
+
OUT
OUT
–
66002 F01
66002 F03
+
–
66002 F02
LT6600-20
t
t
66002f
7