EL8176 INTERSIL [Intersil Corporation], EL8176 Datasheet - Page 11

• Manufacturer Part Number: EL8176
• Description: Micropower Single Supply Rail-to-Rail Input-Output Precision Op Amp
• Manufacturer: INTERSIL [Intersil Corporation]

Proper Layout Maximizes Performance
To achieve the maximum performance of the high input
impedance and low offset voltage of the EL8176, care
should be taken in the circuit board layout. The PC board
surface must remain clean and free of moisture to avoid
leakage currents between adjacent traces. Surface coating
of the circuit board will reduce surface moisture and provide
a humidity barrier, reducing parasitic resistance on the
board. The use of guard rings around the amplifier inputs will
further reduce leakage currents. Figure 40 shows how the
guard ring should be configured and Figure 41 shows the top
view of how a surface mount layout can be arranged. The
guard ring does not need to be a specific width, but it should
form a continuous loop around both inputs. By setting the
guard ring voltage equal to the voltage at the non-inverting
input, parasitic capacitance is minimized as well. For further
reduction of leakage currents, components can be mounted
to the PC board using Teflon standoff insulators.
HIGH IMPEDANCE INPUT
IN
FIGURE 40.
FIGURE 41.
3
4
11
6
2
V+
5
EL8176
1
EL8176
Typical Applications
Thermocouples are the most popular temperature-sensing
device because of their low cost, interchangeability, and
ability to measure a wide range of temperatures. The
EL8176 is used to convert the differential thermocouple
voltage into single-ended signal with 10X gain. The
EL8176's rail-to-rail input characteristic allows the
thermocouple to be biased at ground and the converter to
run from a single 5V supply.
THERMOCOUPLE
K TYPE
FIGURE 42. THERMOCOUPLE AMPLIFIER
R
R
3
2
10kΩ
10kΩ
100kΩ
R
4
+
-
EL8176
100kΩ
R
1
V+
V-
+
5V
October 26, 2006
410µV/°C
FN7436.6