LT1567 View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LT1567' PDF : 16 Pages View PDF
LT1567
APPLICATIO S I FOR ATIO
The simple-to-use spreadsheet requires the user to de-
fine the desired corner (or center) frequency, the pass-
band gain and a capacitor value for a choice of second or
third order Chebyshev or Butterworth lowpass or second
order bandpass filters.
The spreadsheet outputs the required external standard
component values and provides a circuit diagram.
Signal Ground
Both operational amplifiers within the LT1567 are de-
signed for inverting operation (constant common mode
input) and they share a single reference node on the chip.
Two pins permit access to this node: DC BIAS and
BYPASS. For a clean reference over a wide bandwidth, the
normal procedure is to connect DC BIAS to a DC potential
or ground and BYPASS to a decoupling capacitor that
returns to a ground plane.
Differential Output Feature
The multiple feedback filter section of Figure 1 inherently
includes two outputs of opposite signal polarity: a DC
inverting output from the OA (Pin 1) and a DC noninverting
16
VOUT–
R1
VIN
C2 R3 LT1567
C1
2
–
R2
+
0.1µF
3
5
150Ω
V+
600Ω
600Ω
–
+
7pF
V–
DESIGN EQUATIONS FOR fCENTER ≤ 1MHz
fCENTER IS THE FILTER’S CENTER FREQUENCY
7
VOUT+
MAXIMUM fCENTER = 5MHz/GAIN
GN IS GAIN AT fCENTER = R3/R1, R2 = R3, C1 = C2
fCENTER
=
2
√GN + 1
• π • R2 •
C1
–3dB BANDWIDTH = fCENTER
√GN + 1
C1 ≤
√GN + 1
2500 • fC
R3 =
√GN + 1
2π • C1 • fCENTER
8 0.1µF
4 0.1µF
V+
V–
1567 F02a
Gain vs Frequency
25
20
15
10
5
0
–5
–10
–15
50k
500k
FREQUENCY (Hz)
5M
1567 F02b
GAIN IS MEASURED TO EITHER OUTPUT ALONE.
IF OUTPUT USED DIFFERENTIALLY, VOUT+ – VOUT– = 2× VIN
Figure 2. 2nd Order Bandpass Filter and Gain Response for fC = 500kHz,
Gain = 10 (C1 = C2 = 1000pF, R2 = R3 = 1.05k, R1 = 105Ω)
1567fa
9
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