LT1630 Linear Technology, LT1630 Datasheet - Page 14

• Manufacturer Part Number: LT1630
• Description: 30MHz/ 10V/us/ Dual/Quad Rail-to-Rail Input and Output Precision Op Amps
• Manufacturer: Linear Technology

TYPICAL APPLICATIONS
LT1630/LT1631
Single Supply, 40dB Gain, 350kHz
Instrumentation Amplifier
An instrumentation amplifier with a rail-to-rail output
swing, operating from a 3V supply can be constructed with
the LT1630 as shown in Figure 2. The amplifier has a
nominal gain of 100, which can be adjusted with resistor
R5. The DC output level is set by the difference of the two
inputs multiplied by the gain of 100. Common mode range
can be calculated by the equations shown with Figure 2.
For example, the common mode range is from 0.15V to
2.65V if the output is set at one half of the 3V supply. The
common mode rejection is greater than 110dB at 100Hz
when trimmed with resistor R1. The amplifier has a
bandwidth of 355kHz as shown in Figure 3.
BW
14
A
V
OUT
V
Figure 2. Single Supply, 40dB Gain Instrumentation Amplifier
R
R
355
2 0 k
3
R 1
4
V
V
kHz
I N
1
IN
–
R
R
2
1
V
IN
–10
–20
–30
–40
–50
–60
–70
R
50
40
30
20
10
–
+
1 / 2 L T 1 6 3 0
3
0
100
R
5
A
R
Figure 3. Frequency Response
V
V
2
COMMON MODE INPUT
S
DIFFERENTIAL INPUT
R 2
2 k
100
1k
O U T 1
FREQUENCY (Hz)
10k
L O W E R L I M I
UPPER LIMIT COMMON MODE INPUT VOLTAGE
V
V
WHERE V IS THE SUPPLY VOLTAGE
CML
CMH
4 3 2
R 5
R 3
2 k
V
100k
I N
S
V
V
+
A
OUT
OUT
A
U
V
T COMMON MODE INPUT VOLTAGE
V
R
R
R
R
V
A
1M
–
+
2
5
2
5
2 0 k
R 4
1 / 2 L T 1 6 3 0
S
V
= 3V
= 100
1630/31 F03
0 1
1 6 3 0 / 3 1 F 0 2
V
S
V
10M
1 0
1 1
0 15
V
1 0
1 1
V
O U T
4 . 7F
Tunable Q Notch Filter
A single supply, tunable Q notch filter as shown in Figure
4 is built with LT1630 to maximize the output swing. The
filter has a gain of 2, and the notch frequency (f
the values of R and C. The resistors R10 and R11 set up the
DC level at the output. The Q factor can be adjusted by
varying the value of R8. The higher value of R8 will
decrease Q as depicted in Figure 5, because the output
induces less of feedback to amplifier A2. The value of R7
should be equal or greater than R9 to prevent oscillation.
If R8 is a short and R9 is larger than R7, then the positive
feedback from the output will create phase inversion at the
output of amplifier A2, which will lead to oscillation.
C 2
V
R 1 0
I N
1 0 k
5 V
2 . 2F
R 1 1
1 0 k
C 1
R 9
1 k
–20
–40
40
20
0
Figure 4. Tunable Q Notch Filter
0
R 1
5 0 0
Figure 5. Frequency Response
–
1 / 2 L T 1 6 3 0
+
20 40 60
DECREASING R8
1 0 0 0 p F
1 . 6 2 k
A 2
R 2
1 k
f
f
C
R
O
O
98
2
FREQUENCY (kHz)
INCREASING R8
kHz
1
RC
80 100 120
R
1 . 6 2 k
C
1 0 0 0 p F
R 8
5 k
V
A
O DC
V
140 160 180 200
2
R 5
1 k
R
5
11
13630/31 F05
C 5
4 . 7F
V R
+
–
1 / 2 L T 1 6 3 0
R
11
A 1
10
5 V
R 6
1 k
2 5
O
) is set by
V
1 6 3 0 / 3 1 F 0 4
R 7
1 k
V
O U T