EL8178FWZ-T7A 查看數據表（PDF） - Intersil
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EL8178FWZ-T7A Datasheet PDF : 15 Pages
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EL8178
.
HIGH IMPEDANCE INPUT
V+
IN
FIGURE 31. GUARD RING EXAMPLE FOR UNITY GAIN
AMPLIFIER
Typical Applications
GENERAL
PURPOSE
COMBINATION
pH PROBE
+ V+
EL8178
- V-
+
3V
COAX
FIGURE 32. pH PROBE AMPLIFIER
A general-purpose combination pH probe has extremely
high output impedance typically in the range of 10GΩ to
12GΩ. Low loss and expensive Teflon cables are often used
to connect the pH probe to the meter electronics. Figure 32
details a low-cost alternative solution using the EL8178 and
a low-cost coax cable. The EL8178 PMOS high impedance
input senses the pH probe output signal and buffers it to
drive the coax cable. Its rail-to-rail input nature also
eliminates the need for a bias resistor network required by
other amplifiers in the same application.
R3 10kΩ
R2
K TYPE
THERMOCOUPLE
10kΩ
R4
100kΩ
+ V+
EL8178
- V-
+
5V
410μV/°C
R1
100kΩ
FIGURE 33. THERMOCOUPLE AMPLIFIER
Thermocouples are the most popular temperature sensing
devices because of their low cost, interchangeability, and
ability to measure a wide range of temperatures. In
Figure 33, the EL8178 converts the differential thermocouple
voltage into single-ended signal with 10x gain. The EL8178's
rail-to-rail input characteristic allows the thermocouple to be
biased at ground and permits the op amp to operate from a
single 5V supply.
12
FN7504.6
March 17, 2008
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