LT1567CMS8 Просмотр технического описания (PDF) - Linear Technology
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LT1567CMS8 Datasheet PDF : 16 Pages
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LT1567
APPLICATIO S I FOR ATIO
Functional Description
The LT1567 contains two low noise rail-to-rail output,
wideband operational amplifiers, one of them connected
internally as a unity-gain inverter. These two amplifiers
can form a second order multiple feedback filter configu-
ration (Figure 1) for megahertz signal frequencies, with
exceptionally low total noise. The amplifier in the dedi-
cated inverter (INV) is optimized for better high fre-
quency linearity while the uncommitted operational
amplifier (OA) is optimized for lower input noise voltage,
addressing the different sensitivities to these effects
when used as a filter section. This combination produces
a low noise filter with better distortion performance than
would be possible with identical amplifiers.
LT1567 Free Design Software
A spreadsheet-based design tool is available at
www.linear.com for designing lowpass and bandpass
filters using the LT1567.
16
VOUT–
R2
C1 LT1567
R1
R3
2
–
VIN
C2
+
0.1µF
3
5
150Ω
600Ω
600Ω
–
+
7pF
7
VOUT+
V+
8 0.1µF
V–
4 0.1µF
DESIGN EQUATIONS:
( ) GAIN = 1 AND fC ≤ 1MHz
GAIN = R2
R1
fC IS THE FILTER’S CUTOFF FREQUENCY
R1 = R2, C1 = C2, C1 ≤
1
1000 • fC
BUTTERWORTH
R2
=
4.44
1
• C1
•
fC
R3
=
R2
2
CHEBYSHEV
0.25dB
RIPPLE
R2
=
5.65
1
• C1
•
fC
R3
=
R2
2.62
V+
V–
1567 F01a
8
fO
=
1
2π√R2R3
C2
R2
Q
=
R3
GAIN +
1
TRANSFER
FUNCTION
H(s)
=
s2
(2πfO)2
+
(2πfO)
Q
s
+
(2πfO)2
Gain vs Frequency
3
0
–3
–6
–9
–12
–15
–18
–21
–24
–27
–30
100k
BUTTERWORTH
CHEBYSHEV
1M
FREQUENCY (Hz)
10M
1567 F01b
GAIN IS MEASURED TO EITHER OUTPUT ALONE.
IF OUTPUT USED DIFFERENTIALLY, VOUT+ – VOUT– = 2× VIN
Figure 1. 2nd Order Lowpass Filter and Gain Response for fC = 1MHz
(Butterworth: C1 = C2 = 390pF, R1 = R2 = 576Ω, R3 = 280Ω
Chebyshev: C1 = C2 = 390pF, R1 = R2 = 453Ω, R3 = 174Ω)
1567fa
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