INTERSIL EL8178FSZ-T7

EL8178
®
Data Sheet
March 29, 2007
Micropower Single Supply Rail-to-Rail
Input-Output (RRIO) Precision Op Amp
The EL8178 is a precision low power, operational amplifier.
The device is optimized for single supply operation between
2.4V to 5V. This enables operation from one lithium cell or
two Ni-Cd batteries. The input range includes both positive
and negative rail.
For power sensitive applications, the EL8178 has and EN
pin that will shut the device down and reduce the supply
current to 3µA typ. In the active state, the EL8178 draws
minimal supply current (55μA) while meeting excellent DCaccuracy, noise, and output drive specifications.
FN7504.5
Features
• Typical 55μA supply current
• 250μV max offset voltage
• Typical 1pA input bias current
• 266kHz gain-bandwidth product
• Single supply operation between 2.4V to 5.0V
• Rail-to-rail input and output
• Ground sensing
• Output sources and sinks 26mA load current
• Pb-free plus anneal available (RoHS compliant)
Ordering Information
Applications
PART NUMBER
(Note)
PART
MARKING
TAPE &
REEL
EL8178FWZ-T7
BBWA
7”
(3k pcs)
EL8178FWZ-T7A BBWA
PACKAGE
(Pb-free)
PKG.
DWG. #
6 Ld SOT-23 MDP0038
• Battery- or solar-powered systems
• 4mA to 20mA current loops
• Handheld consumer products
7”
6 Ld SOT-23 MDP0038
(250 pcs)
• Medical devices
EL8178FSZ
8178FSZ
97/Tube 8 Ld SO
MDP0027
• Thermocouple amplifiers
EL8178FSZ-T7
8178FSZ
7”
(1k pcs)
MDP0027
• Photodiode pre-amps
8 Ld SO
• pH probe amplifiers
NOTE: Intersil Pb-free plus anneal products employ special Pb-free
material sets; molding compounds/die attach materials and 100%
matte tin plate termination finish, which are RoHS compliant and
compatible with both SnPb and Pb-free soldering operations. Intersil
Pb-free products are MSL classified at Pb-free peak reflow
temperatures that meet or exceed the Pb-free requirements of
IPC/JEDEC J STD-020.
Pinouts
EL8178
(6 LD SOT-23)
TOP VIEW
OUT 1
VS- 2
6 VS+
+ -
IN+ 3
5 EN
4 IN-
EL8178
(8 LD SO)
TOP VIEW
NC 1
IN- 2
IN+ 3
VS- 4
1
8 EN
+
7 VS+
6 OUT
5 NC
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright © Intersil Americas Inc. 2004-2007. All Rights Reserved.
All other trademarks mentioned are the property of their respective owners.
EL8178
Absolute Maximum Ratings (TA = +25°C)
Thermal Information
Supply Voltage (VS) and Pwr-up Ramp Rate . . . . . . . . 5.5V, 1V/μs
Differential Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5V
Current into IN+, IN-, and EN. . . . . . . . . . . . . . . . . . . . . . . . . . . 5mA
Input Voltage . . . . . . . . . . . . . . . . . . . . . . . VS- - 0.5V to VS+ + 0.5V
ESD Tolerance
Human Body Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3kV
Machine Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .300V
Thermal Resistance
θJA (°C/W)
6 Ld SOT Package . . . . . . . . . . . . . . . . . . . . . . . . .
230
8 Ld SO Package . . . . . . . . . . . . . . . . . . . . . . . . . .
110
Ambient Operating Temperature Range . . . . . . . . -40°C to +125°C
Storage Temperature Range . . . . . . . . . . . . . . . . . -65°C to +150°C
Operating Junction Temperature . . . . . . . . . . . . . . . . . . . . . +125°C
Pb-free reflow profile . . . . . . . . . . . . . . . . . . . . . . . . . .see link below
http://www.intersil.com/pbfree/Pb-FreeReflow.asp
CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the
device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
IMPORTANT NOTE: All parameters having Min/Max specifications are guaranteed. Typical values are for information purposes only. Unless otherwise noted, all tests
are at the specified temperature and are pulsed tests, therefore: TJ = TC = TA
Electrical Specifications
PARAMETER
VOS
VS+ = 5V, VS- = 0V, VCM = 2.5V, VO = 2.5V, TA = +25°C unless otherwise specified. Boldface limits apply over
the operating temperature range, -40°C to +125°C
DESCRIPTION
TEST CONDITIONS
Input Offset Voltage
MIN
TYP
MAX
UNIT
-250
50
250
μV
450
μV
-450
ΔV OS
-----------------ΔTime
Long Term Input Offset Voltage
Stability
ΔV OS
---------------ΔT
Input Offset Drift vs Temperature
IB
Input Bias Current
See Figures 18 and 19
-25
3
μV/Mo
1.1
μV/°C
1
-600
25
pA
600
pA
Input Noise Voltage Peak-to-Peak
f = 0.1Hz to 10Hz
2.8
μVP-P
Input Noise Voltage Density
fO = 1kHz
48
nV/√Hz
iN
Input Noise Current Density
fO = 1kHz
0.15
pA/√Hz
CMIR
Input Voltage Range
Guaranteed by CMRR test
0
CMRR
Common-Mode Rejection Ratio
VCM = 0V to 5V
80
eN
5
100
dB
75
PSRR
Power Supply Rejection Ratio
VS = 2.4V to 5V
80
dB
100
dB
80
AVOL
VOUT
Large Signal Voltage Gain
Maximum Output Voltage Swing
VO = 0.5V to 4.5V,
RL = 100kΩ to (VS+ + VS-)/2
100
VOL; Output low,
RL = 1kΩ to (VS+ + VS-)/2
SR
dB
400
V/mV
3
10
mV
130
250
mV
350
mV
VOH; Output high,
RL = 100kΩ to (VS+ + VS-)/2
4.994
4.9975
V
VOH; Output high,
RL = 1kΩ to (VS+ + VS-)/2
4.750
4.875
V
Slew Rate
4.7
0.10
V
0.15
0.07
GBWP
Gain Bandwidth Product
2
V/mV
100
VOL; Output low,
RL = 100kΩ to (VS+ + VS-)/2
V
fO = 100kHz
266
0.19
V/μs
0.25
V/μs
kHz
FN7504.5
March 29, 2007
EL8178
Electrical Specifications
PARAMETER
IS(ON)
VS+ = 5V, VS- = 0V, VCM = 2.5V, VO = 2.5V, TA = +25°C unless otherwise specified. Boldface limits apply over
the operating temperature range, -40°C to +125°C (Continued)
DESCRIPTION
TEST CONDITIONS
MIN
TYP
MAX
UNIT
35
55
75
μA
85
μA
5
μA
Supply Current, Enabled
30
IS(OFF)
Supply Current, Disabled
3
ISC+
Short Circuit Output Sourcing Current RL = 10Ω to opposite supply
23
31
mA
18
ISC-
Short Circuit Output Sinking Current
RL = 10Ω to opposite supply
mA
20
26
mA
15
Minimum Supply Voltage
VS
Guaranteed by PSRR
2.2
VINH
EN Pin High Level
VINL
EN Pin Low Level
IENH
EN Pin Input Current
VEN = 5V
0.25
IENL
EN Pin Input Current
VEN = 0V
-0.5
2.4
V
2.4
V
2
Typical Performance Curves
V
0.8
0.8
V
2.5
μA
+0.5
μA
VS = ±2.5V, TA = +25°C, Unless Otherwise Specified
1
80
RL ≥ 10kΩ
VOUT = 0.2VP-P
RL ≥ 10kΩ
VOUT = 0.2VP-P
GAIN = 1k
70
GAIN = 500
60
0
50
VS = ±1.25
GAIN (dB)
GAIN (dB)
mA
-1
VS = ±2.5V
GAIN = 200
40
GAIN = 100
GAIN = 10
30
GAIN = 5
20
10
-2
GAIN = 2
0
VS = ±1.0V
-3
1k
10k
-10
100k
GAIN = 1
-20
1M
1
10
100
FREQUENCY (Hz)
10k
100k 1M
10M
FREQUENCY (Hz)
FIGURE 1. UNITY GAIN FREQUENCY RESPONSE at
VARIOUS SUPPLY VOLTAGES
FIGURE 2. FREQUENCY RESPONSE at VARIOUS CLOSED
LOOP GAINS
60
200
INPUT OFFSET VOLTAGE (μV)
SUPPLY CURRENT (μA)
1k
50
40
30
20
10
0
2
2.5
3
3.5
4
4.5
5
5.5
SUPPLY VOLTAGE (V)
FIGURE 3. SUPPLY CURRENT vs SUPPLY VOLTAGE
3
AV = -1
VCM = VDD/2
100
0
-100
-200
-0.5
0.5
1.5
2.5
3.5
4.5
5.5
OUTPUT VOLTAGE (V)
FIGURE 4. INPUT OFFSET VOLTAGE vs OUTPUT VOLTAGE
FN7504.5
March 29, 2007
EL8178
250
100
150
80
0
60
45
50
-50
PHASE
90
40
20
-150
-250
-0.5
180
0
0.5
1.5
2.5
3.5
4.5
-20
10
5.5
10
90
0
80
-10
90
PHASE
135
30
20
180
GAIN
ΔVCM = 1VP-P
RL = 100kΩ
AV = +1
-20
CMRR (dB)
60
PHASE SHIFT (°)
-30
-40
-50
-60
-70
-80
0
-90
-10
10
100
1k
10k
100k
-100
10
1M
100
FREQUENCY (Hz)
1k
100k
FIGURE 8. CMRR vs FREQUENCY
100
1000
10
VOLTAGE NOISE (nV/√Hz)
ΔVS = 1VP-P
0
RL = 100kΩ
-10
AV = +1
-20
-30
-PSRR
-40
-50
+PSRR
-60
1M
FREQUENCY (Hz)
FIGURE 7. OPEN LOOP GAIN AND PHASE vs FREQUENCY
(RL = 100kΩ)
-70
-80
10
100
VOLTAGE
1
10
CURRENT
-90
-100
10
10k
CURRENT NOISE (pA/√Hz)
GAIN (dB)
70
10
1M
FIGURE 6. OPEN LOOP GAIN AND PHASE vs FREQUENCY
(RL = 1kΩ)
100
40
100k
10k
FREQUENCY (Hz)
FIGURE 5. INPUT OFFSET VOLTAGE vs COMMON-MODE
INPUT VOLTAGE
50
1k
100
COMMON-MODE INPUT VOLTAGE (V)
PSRR (dB)
135
GAIN
PHASE SHIFT (°)
(Continued) VS = ±2.5V, TA = +25°C, Unless Otherwise Specified (Continued)
GAIN (dB)
NORMALIZED INPUT OFFSET VOLTAGE (μV)
Typical Performance Curves
100
1k
10k
100k
FREQUENCY (Hz)
FIGURE 9. PSRR vs FREQUENCY
4
1M
1
1
10
100
1k
10k
0.1
100k
FREQUENCY (Hz)
FIGURE 10. INPUT VOLTAGE AND CURRENT NOISE vs
FREQUENCY
FN7504.5
March 29, 2007
EL8178
Typical Performance Curves
(Continued) VS = ±2.5V, TA = +25°C, Unless Otherwise Specified (Continued)
20
10
VOS DRIFT (µV)
VOLTAGE NOISE (500nV/DIV)
15
5
0
-5
2.8μVP-P
-10
-15 0
500
TIME (1s/DIV)
FIGURE 11. 0.1Hz TO 10Hz INPUT VOLTAGE NOISE
1000
TIME (HOURS)
1500
1800
FIGURE 12. IVOS DRIFT (SOT-23 PACKAGE) vs TIME
75
18
n = 1500
MAX
70
13
CURRENT (mA)
VOS DRIFT (µV)
65
8
3
-2
MEDIAN
60
55
50
MIN
45
-7
-12
40
0
500
1000
35
-40
1500
-20
0
TIME (HOURS)
20
40
60
80
100
120
TEMPERATURE (°C)
FIGURE 13. IVOS DRIFT (SOIC PACKAGE) vs TIME
FIGURE 14. ENABLED SUPPLY CURRENT vs
TEMPERATURE, VS = ±2.5V
5.0
400
n = 1500
n = 1500
MAX
300
MAX
4.5
VIO (µV)
CURRENT (mA)
200
4.0
3.5
0
MEDIAN
-100
3.0
MEDIAN
-200
MIN
2.5
-300
MIN
2.0
-40
100
-20
0
20
40
60
80
TEMPERATURE (°C)
FIGURE 15. DISABLED SUPPLY CURRENT vs
TEMPERATURE, VS = ±2.5V
5
100
120
-400
-40
-20
0
20
40
60
80
100
120
TEMPERATURE (°C)
FIGURE 16. VOS vs TEMPERATURE, VS = ±2.5V
FN7504.5
March 29, 2007
EL8178
Typical Performance Curves
(Continued) VS = ±2.5V, TA = +25°C, Unless Otherwise Specified (Continued)
800
600
160
n = 1500
MAX
MAX
120
200
IBIAS + (pA)
400
VIO (μV)
n = 1500
140
MEDIAN
0
-200
-400
100
80
60
MEDIAN
40
20
MIN
MIN
-600
0
-800
-40
-20
0
20
40
60
80
100
-20
-40
120
-20
0
TEMPERATURE (°C)
80
100
120
FIGURE 18. IBIAS+ vs TEMPERATURE, VS = ±2.5V
125
MAX
n = 1500
120
MAX
115
MEDIAN
CMRR (dB)
IBIAS -(pA)
60
130
110
105
MEDIAN
100
95
90
20
40
60
80
TEMPERATURE (°C)
100
MIN
85
MIN
80
-40
120
-20
0
20
40
60
80
100
120
TEMPERATURE (°C)
FIGURE 19. IBIAS- vs TEMPERATURE, VS = ±2.5V
FIGURE 20. CMRR vs TEMPERATURE, V+ = ±2.5V, ±1.5V
130
125
40
TEMPERATURE (°C)
FIGURE 17. VOS vs TEMPERATURE, VS = ±1.2V
250
n = 1500
230
210
190
170
150
130
110
90
70
50
30
10
-10
-40 -20
0
20
4.90
n = 1500
MAX
n = 1500
4.89
MAX
115
4.88
VOUT (V)
PSRR (dB)
120
110
MEDIAN
105
100
4.87
MEDIAN
4.86
95
MIN
4.85
90
85
-40
MIN
-20
0
20
40
60
80
100
120
TEMPERATURE (°C)
FIGURE 21. PSRR vs TEMPERATURE ±1.5V TO ±2.5V
6
4.84
-40
-20
0
20
40
60
80
100
120
TEMPERATURE (°C)
FIGURE 22. VOUT HIGH vs TEMPERATURE, VS = ±2.5V, RL = 1k
FN7504.5
March 29, 2007
EL8178
Typical Performance Curves
(Continued) VS = ±2.5V, TA = +25°C, Unless Otherwise Specified (Continued)
4.9984
190
n = 1500
4.9982
4.9980
MAX
170
VOUT (mV)
MAX
4.9978
VOUT (V)
n = 1500
180
4.9976
4.9974
MEDIAN
4.9972
160
MEDIAN
150
140
MIN
130
4.9970
120
4.9968
MIN
4.9966
110
4.9964
100
-40
-20
0
20
40
60
80
100
-40
120
-20
0
FIGURE 23. VOUT HIGH vs TEMPERATURE, VS = ±2.5V,
RL = 100k
40
60
80
100
120
FIGURE 24. VOUT LOW vs TEMPERATURE, VS = ±2.5V,
RL = 1k
510
5.0
4.8
20
TEMPERATURE (°C)
TEMPERATURE (°C)
n = 1500
n = 1500
MAX
460
MAX
4.6
410
MEDIAN
AVOL (V/mV)
VOUT (mV)
4.4
4.2
4.0
MIN
3.8
360
MEDIAN
310
260
3.6
3.4
MIN
210
3.2
160
3.0
-40
-20
0
20
40
60
80
100
120
TEMPERATURE (°C)
FIGURE 25. VOUT LOW vs TEMPERATURE, VS = ±2.5V,
RL = 100k
7
-40
-20
0
20
40
60
80
100
120
TEMPERATURE (°C)
FIGURE 26. AVOL vs TEMPERATURE, RL = 100k, VO = ±2V @
VS = ±2.5V
FN7504.5
March 29, 2007
EL8178
Pin Descriptions
SO PIN
NUMBER
SOT-23 PIN
NUMBER
PIN NAME
1
EQUIVALENT
CIRCUIT
NC
DESCRIPTION
No internal connection
2
4
IN-
Circuit 1
Amplifier’s inverting input
3
3
IN+
Circuit 1
Amplifier’s non-inverting input
4
2
VS-
Circuit 4
Negative power supply
5
NC
No internal connection
6
1
OUT
Circuit 3
Amplifier’s output
7
6
VS+
Circuit 4
Positive power supply
8
5
EN
Circuit 2
Amplifier’s enable pin with internal pull-down; Logic “1” selects the disabled state;
Logic “0” selects the enabled state.
VS+
VS+
IN-
IN+
CAPACITIVELY
COUPLED
ESD CLAMP
VS-
VS-
CIRCUIT 2
Application Information
Introduction
The EL8178 is a rail-to-rail input and output (RRIO),
micro-power, precision, single supply op amp with an enable
feature. This amplifier is designed to operate from single
supply (2.4V to 5.0V) or dual supply (±1.2V to ±2.5V) while
drawing only 55μA of supply current.The device achieves
rail-to-rail input and output operation while eliminating the
drawbacks of many conventional RRIO op amps.
Rail-to-Rail Input
The PFET input stage of the EL8178 has an input
common-mode voltage range that includes the negative and
positive supplies without introducing offset errors or
degrading performance like some existing rail-to-rail input op
amps. Many rail-to-rail input stages use two differential input
pairs: a long-tail PNP (or PFET) and an NPN (or NFET).
Severe penalties result from using this topology. As the input
signal moves from one supply rail to the other, the op amp
switches from one input pair to the other causing changes in
input offset voltage and an undesired change in the input
offset current’s magnitude and polarity.
The EL8178 achieves rail-to-rail input performance without
sacrificing important precision specifications and without
degrading distortion performance. The EL8178's input offset
voltage exhibits a smooth behavior throughout the entire
common-mode input range.
8
VS+
OUT
EN
VS-
CIRCUIT 1
VS+
VSCIRCUIT 3
CIRCUIT 4
Rail-to-Rail Output
A pair of complementary MOSFET devices achieves rail-to-rail
output swing. The NMOS sinks current to swing the output in
the negative direction, while the PMOS sources current to
swing the output in the positive direction. The EL8178 with a
100kΩ load swings to within 3mV of the supply rails.
Results of Over-Driving the Output
Caution should be used when over-driving the output for long
periods of time. Over-driving the output can occur in three
ways:
1. The input voltage times the gain of the amplifier exceeds the
supply voltage by a large value.
2. The output current required is higher than the output stage
can deliver.
3. Operating the device in Slew Rate Limit. These conditions
can result in a shift in the Input Offset Voltage (VOS) as
much as 1µV/hr of exposer under these condition.
Enable/Disable Feature
The EL8178 features an active low EN pin that when pulled
up to at least 2V, disables the output and drops the ICC to a
3µA. The EN pin has an internal pull down, so an undriven
pin pulls to the negative rail, thereby enabling the op amp by
default. For applications where the EN pin is not being used,
it is recommended that the EN pin be permanently tie to
ground.
The high impedance output during disable allows for
connecting multiple EL8178s together to implement a Mux
Amp. The outputs are connected together and activating the
appropriate EN pin selects the desired channel. If utilizing
FN7504.5
March 29, 2007
EL8178
non-unity gain op amp configurations, then the loading
effects of the disabled amplifiers’ feedback networks must be
considered when evaluating the active amplifier’s
performance in Mux Amp configurations.
Note that feed through from the IN+ to IN- pins occurs on
any Mux Amp disabled channel where the input differential
voltage exceeds 0.5V (e.g., active channel VOUT = 1V, while
disabled channel VIN = GND), so the mux implementation is
best suited for small signal applications. In any application
where two or more amplifier outputs are muxed, use series
IN+ resistors, or large value RFs in each amplifier to keep
the feed through current low enough to minimize the impact
on the active channel. See “Usage Implications” on page 9
for more details.
IN+ and IN- Input Protection
In addition to ESD protection diodes to each supply rail, the
EL8178 has additional back-to-back protection diodes across
the differential input terminals (see “Circuit 1” diagram on
page 8). If the magnitude of the differential input voltage
exceeds the diode’s VF, then one of these diodes will conduct.
For elevated temperatures, the leakage of the protection
diodes (Circuit 1 pin description table) increases, resulting in
the increase in Ibias as seen in Figures 18 and 19.
Usage Implications
EN Input Protection
The EN input has internal ESD protection diodes to both the
positive and negative supply rails, limiting the input voltage
range to within one diode beyond the supply rails (see “Circuit
2” diagram on page 8). If the input voltage is expected to
exceed VS+ or VS-, then an external series resistor should be
added to limit the current to 5mA.
Output Current Limiting
The EL8178 has no internal current-limiting circuitry. If the
output is shorted, it is possible to exceed the “Absolute
Maximum Rating” for “operating junction temperature”,
potentially resulting in the destruction of the device.
Power Dissipation
It is possible to exceed the +150°C maximum junction
temperature (TJMAX) under certain load and power-supply
conditions. It is therefore important to calculate TJMAX for all
applications to determine if power supply voltages, load
conditions, or package type need to be modified to remain in
the safe operating area. These parameters are related as
follows:
T JMAX = T MAX + ( θ JA xPDMAX )
(EQ. 1)
where PDMAX is calculated using:
If the input differential voltage is expected to exceed 0.5V, an
external current limiting resistor must be used to ensure the
input current never exceeds 5mA. For noninverting unity gain
applications the current limiting can be via a series IN+ resistor,
or via a feedback resistor of appropriate value. For other gain
configurations, the series IN+ resistor is the best choice, unless
the feedback (RF) and gain setting (RG) resistors are both
sufficiently large to limit the input current to 5mA.
V OUTMAX
PD MAX = V S × I SMAX + ( V S - V OUTMAX ) × ---------------------------R
L
(EQ. 2)
where:
• TMAX = Maximum ambient temperature
• θJA = Thermal resistance of the package
Large differential input voltages can arise from several
sources:
• PDMAX = Maximum power dissipation of the amplifier
1) During open loop (comparator) operation. The IN+ and INinput voltages don’t track.
• IMAX = Maximum supply current of the amplifier
2) When the amplifier is disabled but an input signal is still
present. An RL or RG to GND keeps the IN- at GND, while
the varying IN+ signal creates a differential voltage. Mux
Amp applications are similar, except that the active channel
VOUT determines the voltage on the IN- terminal.
3) When the slew rate of the input pulse is considerably
faster than the op amp’s slew rate. If the VOUT can’t keep up
with the IN+ signal, a differential voltage results, and visible
distortion occurs on the input and output signals. To avoid
this issue, keep the input slew rate below 0.2V/μs, or use
appropriate current limiting resistors.
Large (>2V) differential input voltages can also cause an
increase in disabled ICC.
9
• VS = Supply voltage
• VOUTMAX = Maximum output voltage swing of the
application
• RL = Load resistance
Proper Layout Maximizes Precision
To achieve the optimum levels of high input impedance (i.e.,
low input currents) and low offset voltage, 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. When input
leakage current is a paramount concern, the use of guard
rings around the amplifier inputs will further reduce leakage
currents. Figure 27 shows a guard ring example for a unity
gain amplifier that uses the low impedance amplifier output
at the same voltage as the high impedance input to eliminate
surface leakage. The guard ring does not need to be a
FN7504.5
March 29, 2007
EL8178
specific width, but it should form a continuous loop around
both inputs. For further reduction of leakage currents, mount
components to the PC board using Teflon standoffs.
V+
HIGH IMPEDANCE INPUT
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.
IN
R4
100kΩ
FIGURE 27. GUARD RING EXAMPLE FOR UNITY GAIN
AMPLIFIER
Typical Applications
GENERAL
PURPOSE
COMBINATION
pH PROBE
R3
10kΩ
R2
K TYPE
THERMOCOUPLE
10kΩ
VS+
+
EL8178
VS-
410μV/°C
+
5V
R1
VS+
+
EL8178
VS-
100kΩ
FIGURE 29. THERMOCOUPLE AMPLIFIER
+
3V
COAX
FIGURE 28. 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 28
details a low-cost alternative solution using the EL8178 and
10
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 29, 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.
FN7504.5
March 29, 2007
EL8178
Small Outline Package Family (SO)
A
D
h X 45°
(N/2)+1
N
A
PIN #1
I.D. MARK
E1
E
c
SEE DETAIL “X”
1
(N/2)
B
L1
0.010 M C A B
e
H
C
A2
GAUGE
PLANE
SEATING
PLANE
A1
0.004 C
0.010 M C A B
L
b
0.010
4° ±4°
DETAIL X
MDP0027
SMALL OUTLINE PACKAGE FAMILY (SO)
INCHES
SYMBOL
SO-14
SO16 (0.300”)
(SOL-16)
SO20
(SOL-20)
SO24
(SOL-24)
SO28
(SOL-28)
TOLERANCE
NOTES
A
0.068
0.068
0.068
0.104
0.104
0.104
0.104
MAX
-
A1
0.006
0.006
0.006
0.007
0.007
0.007
0.007
±0.003
-
A2
0.057
0.057
0.057
0.092
0.092
0.092
0.092
±0.002
-
b
0.017
0.017
0.017
0.017
0.017
0.017
0.017
±0.003
-
c
0.009
0.009
0.009
0.011
0.011
0.011
0.011
±0.001
-
D
0.193
0.341
0.390
0.406
0.504
0.606
0.704
±0.004
1, 3
E
0.236
0.236
0.236
0.406
0.406
0.406
0.406
±0.008
-
E1
0.154
0.154
0.154
0.295
0.295
0.295
0.295
±0.004
2, 3
e
0.050
0.050
0.050
0.050
0.050
0.050
0.050
Basic
-
L
0.025
0.025
0.025
0.030
0.030
0.030
0.030
±0.009
-
L1
0.041
0.041
0.041
0.056
0.056
0.056
0.056
Basic
-
h
0.013
0.013
0.013
0.020
0.020
0.020
0.020
Reference
-
16
20
24
28
Reference
-
N
SO-8
SO16
(0.150”)
8
14
16
Rev. M 2/07
NOTES:
1. Plastic or metal protrusions of 0.006” maximum per side are not included.
2. Plastic interlead protrusions of 0.010” maximum per side are not included.
3. Dimensions “D” and “E1” are measured at Datum Plane “H”.
4. Dimensioning and tolerancing per ASME Y14.5M-1994
11
FN7504.5
March 29, 2007
EL8178
SOT-23 Package Family
MDP0038
e1
D
SOT-23 PACKAGE FAMILY
A
MILLIMETERS
6
N
SYMBOL
4
E1
2
E
3
0.15 C D
1
2X
2
3
0.20 C
5
2X
e
0.20 M C A-B D
B
b
NX
0.15 C A-B
1
3
SOT23-5
SOT23-6
TOLERANCE
A
1.45
1.45
MAX
A1
0.10
0.10
±0.05
A2
1.14
1.14
±0.15
b
0.40
0.40
±0.05
c
0.14
0.14
±0.06
D
2.90
2.90
Basic
E
2.80
2.80
Basic
E1
1.60
1.60
Basic
e
0.95
0.95
Basic
e1
1.90
1.90
Basic
L
0.45
0.45
±0.10
L1
0.60
0.60
Reference
N
5
6
Reference
D
2X
Rev. F 2/07
NOTES:
C
A2
2. Plastic interlead protrusions of 0.25mm maximum per side are not
included.
SEATING
PLANE
A1
0.10 C
1. Plastic or metal protrusions of 0.25mm maximum per side are not
included.
3. This dimension is measured at Datum Plane “H”.
4. Dimensioning and tolerancing per ASME Y14.5M-1994.
NX
5. Index area - Pin #1 I.D. will be located within the indicated zone
(SOT23-6 only).
(L1)
6. SOT23-5 version has no center lead (shown as a dashed line).
H
A
GAUGE
PLANE
c
L
0.25
0° +3°
-0°
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12
FN7504.5
March 29, 2007