LT1567I View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LT1567I' PDF : 16 Pages View PDF
LT1567
APPLICATIO S I FOR ATIO
Figure 4 shows an LT1567 single supply differential buffer
driving a differential 1st order RC filter. The VREF voltage
is subject to the common mode (DC BIAS) limits in the
spec table. Within this constraint, VREF can be used to
adjust the output common mode level, as noted in Figure
4. For example, in a single 5V power supply circuit, if the
input common mode DC voltage is 1.1V and VREF is 1.8V,
then the output common mode DC voltage is 2.5V.
Figure 5 shows a low noise differential to single ended
amplifier and 1st order lowpass filter. The input common
mode rejection depends on the matching of resistors R1
and R3 and the LT1567 inverter gain tolerance (common
mode rejection is at least 38dB up to 1MHz with 1%
resistors and 5% inverter gain tolerance). The DC voltage
at the amplifier’s output (VOUT) is VREF.
Output Drive
The output of the LT1567 op amp (Pin 1) can typically
provide at least ±20mA. The minimum resistive load to
ground that Pin 1 or Pin 7 can drive depends on the
feedback resistor and the peak output voltage. For ex-
ample, the differential driver circuit in Figure 4 is operating
with a single 5V supply, VREF and VINDC are equal to 2.5V
and the peak AC signal (VINAC) is 1V. If the outputs provide
1.66mA to the feedback resistors (1V/604Ω), then 18.34mA
is available to drive a resistive load. With the peak output
voltage at 3.5V (2.5V DC plus 1V peak AC), the outputs can
drive resistive loads of 191Ω or greater.
VIN1
604Ω
VIN2
604Ω
LT1567
2
–
16
600Ω
600Ω
0.1µF
3
5
VREF
+
–
7pF
150Ω
V+
8 0.1µF
+
V–
4
VOUT1
R
7 VOUT2 R
1567 F04a
V+
VOUT1 = –VIN2 + 2VREF
VOUT2 = –VIN1 + 2VREF
COMMON MODE VOUT IS 2VREF – (COMMON MODE VIN)
VDIFF = VOUT2 – VOUT1 = VIN2 – VIN1
f–3dB
=
4π
1
•R
•
C
fηBW IS THE NOISE BANDWIDTH
fηBW =
1.57
4π • R • C
C VDIFF
Figure 4. A Differential Buffer/Driver
1567fa
12
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