LT1633 Linear Technology, LT1633 Datasheet - Page 14

• Manufacturer Part Number: LT1633
• Description: 45MHz/ 45V/us/ Dual/Quad Rail-to-Rail Input and Output Precision Op Amps
• Manufacturer: Linear Technology

V
V
LT1632/LT1633
14
TYPICAL APPLICATIONS
S
Common mode range can be calculated by the following
equations:
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 550kHz.
Single Supply, 400kHz, 4th Order Butterworth Filter
The circuit shown in Figure 2 makes use of the low voltage
operation and the wide bandwidth of the LT1632 to create
a 400kHz 4th order lowpass filter with a single supply. The
amplifiers are configured in the inverting mode to mini-
mize common mode induced distortion and the output
can swing rail-to-rail for the maximum dynamic range.
Figure 3 displays the frequency response of the filter.
Stopband attenuation is greater than 85dB at 10MHz.
IN
/2
Figure 2. Single Supply, 400kHz, 4th Order Butterworth Filter
Lower
Upper
A
V
V
V
where V
2.32k
CML
CMH
OUT
V
2.32k
R
R
6.65k
220pF
limit common mode input voltage
limit common mode input voltage
4
3
S
V
is supply voltage.
1
IN
V
V
OUT
A
OUT
A
47pF
V
V
–
+
R
1/2 LT1632
R
2
1
V
IN
R
R
R
R
2
5
R
2
5
3
R
0 1
5
A
V
R
2.74k
V
S
2
V
1 0
0 15
1 1
U
2.74k
5.62k
470pF
V
1 0
22pF
1 1
–
+
1/2 LT1632
1632/33 F02
V
OUT
0.01 F
With a 2.25V
filter has harmonic distortion of less than – 87dBc.
RF Amplifier Control Biasing and DC Restoration
Taking advantage of the rail-to-rail input and output, and
the large output current capability of the LT1632, the
circuit shown in Figure 4 provides precise bias current for
the RF amplifiers and restores the DC output level. To
ensure optimum performance of an RF amplifier, its bias
point must be accurate and stable over the operating
C1
V
Figure 4. RF Amplifier Control Biasing and DC Restoration
IN
+
L3
3.9 H
R2
453
R3
10k
R5
50
1500pF
–10
–20
–30
–40
–50
–60
–70
–80
–90
C2
10
P-P
0
0.1k
HP-MSA0785
–
+
1/2 LT1632
Figure 3. Frequency Response
, 100kHz input signal on a 3V supply, the
V
V
S
IN
A1
RF1
= 3V, 0V
= 2.5V
5V
1k
P-P
FREQUENCY (Hz)
–
+
1/2 LT1632
10k
5V
A2
L1
220 H
R1
10
Q1
2N3906
1500pF
C3
100k
+
HP-MSA0785
C5
0.01 F
RF2
1M
1632/33 F03
10M
Q2
2N3906
L2
220 H
R4
10
1500pF
C4
+
L4
3.9 H
1632/33 F04
C6
0.01 F
V
OUT