LTC6257 Linear Technology, LTC6257 Datasheet - Page 15

• Manufacturer Part Number: LTC6257
• Description: 65uA Power Efficient Rail-to-Rail I/O Op Amps
• Manufacturer: Linear Technology

typicAl ApplicAtions
LTC6255 Very Low Power 2nd Order Lowpass Filter
The LTC6256 circuit shown in Figure 4 is a 2nd order,
100kHz, Butterworth lowpass filter. The filter’s differential
output maximizes the dynamic range in very low voltage
operation. A general 2nd order lowpass circuit is shown in
V
IN
2.49k
10k
V
2.49k
IN
1000pF
(Single-Ended Input and Differential Output)
10k
1.8V
A, 1.8V, 140µA, 100kHz, Lowpass Filter
200kHz 130µA Gain-of-100 Amplifier
+
–
1/2 LTC6256
Figure 3. Gain of 100 Amplifier (3dB Bandwidth of 200kHz on 130µA Supply Current)
10µF
100k
100k
100pF
–0.9V
0.9V
90.9k
2
3
–
1/2 LTC6256
+
10k
1.8V
8
0.1µF
–
+
1/2 LTC6256
1
90.9k
625567 F03a
2.49k
6
5
–
+
1/2 LTC6256
2.49k
4
V
OUT
Figure 4
7
Figure 5 with the equations to calculate the RC components
for cutoff frequencies up to 100kHz for a Butterworth or a
Bessel approximation (a Bessel lowpass filter has very low
transient response overshoot). In addition the equations
for a 4th order lowpass filter are provided to calculate the
RC components for two cascaded 2nd order sections.
625567 F04a
LTC6255/LTC6256/LTC6257
V
V
OUT
OUT
–
+
–10
–20
–30
–40
–50
50
40
30
20
10
0
10
Frequency Response of 40dB
100
–12
–18
–24
–30
–36
–42
Gain Amplifier
1k
–6
FREQUENCY (Hz)
6
0
10k
10k
Frequency Response
100k
FREQUENCY (Hz)
1M
100k
625567 F03b
www.DataSheet4U.com
10M
625567 F04b

1M
625567f