Datasheet

LTC6255/LTC6256/LTC6257
625567fb
15
50
–10
40
20
0
–30
30
10
–40
–20
–50
GAIN (dB)
625567 F03b
FREQUENCY (Hz)
10 100 100k 10M1M10k1k
typicAl ApplicAtions
90.9k 90.9k
V
IN
625567 F03a
V
OUT
0.9V
–0.9V
–
+
–
+
10k 10k
1/2 LTC6256
1/2 LTC6256
Frequency Response of 40dB
Gain Amplifier
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
Figure 3. Gain of 100 Amplifier (3dB Bandwidth of 200kHz on 130µA Supply Current)
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.
200kHz 130µA Gain-of-100 Amplifier
A, 1.8V, 140µA, 100kHz, Lowpass Filter
(Single-Ended Input and Differential Output) Frequency Response
FREQUENCY (Hz)
GAIN (dB)
625567 F04b
10k 100k 1M
6
–18
–30
–6
–42
–12
–24
0
–36
–
+
–
+
7
V
OUT
+
625567 F04a
V
OUT
–
2.49k
1/2 LTC6256
1/2 LTC6256
2
1
100pF
3
5
6
8
V
IN
1000pF
10k
1.8V
1.8V
2.49k
2.49k
2.49k
0.1µF
4
10µF
100k
100k
Figure 4