100nV/div
Time(1s/div)Time(1s/div)
0.1HzTO10HzNOISE
Frequency(Hz)
NOISESPECTRALDENSITYvsFREQUENCY
1
VoltageNoiseDensity(nV/ )ÖHz
CurrentNoise(fA/ )ÖHz
Frequency(Hz)
10 100 1k 10k
1k
100
10
1
CurrentNoise
VoltageNoise
ContinueswithNo1/f(flicker)Noise
OPA378
OPA2378
www.ti.com
SBOS417D –JANUARY 2008–REVISED OCTOBER 2009
Low-Noise, 900kHz, RRIO,
Precision OPERATIONAL AMPLIFIER
Zerø-Drift Series
Check for Samples: OPA378 OPA2378
1FEATURES DESCRIPTION
23• LOW NOISE The OPA378 and OPA2378 represent a new
generation of Zerø-Drift, microPOWER™ operational
– 0.4μVPP, 0.1Hz to 10Hz amplifiers that use a proprietary auto-calibration
– 20nV/√Hz at 1kHz technique to provide minimal input offset voltage
• ZERØ-DRIFT SERIES (20μV) and offset voltage drift (0.1μV/°C). The
– LOW OFFSET VOLTAGE: 20μVcombination of low input voltage noise, high gain
bandwidth (900kHz), and low power (150μA max)
– LOW OFFSET DRIFT: 0.1μV/°C enable these devices to achieve optimum
• QUIESCENT CURRENT: 125μAperformance for low-power precision applications. In
• GAIN BANDWIDTH: 900kHz addition, the excellent PSRR performance, coupled
with a wide input supply range of 2.2V to 5.5V and
• RAIL-TO-RAIL INPUT/OUTPUT rail-to-rail input and output, makes it an outstanding
• EMI FILTERING choice for single-supply applications that run directly
• SUPPLY VOLTAGE: 2.2V to 5.5V from batteries without regulation.
•microSIZE PACKAGES: SC70 and SOT23 The OPA378 (single version) is available in both a
microSIZE SC70-5 and a SOT23-5 package. The
APPLICATIONS OPA2378 (dual version) is offered in a SOT23-8
package. All versions are specified for operation from
• PORTABLE MEDICAL DEVICES –40°C to +125°C.
– GLUCOSE METERS
– OXYGEN METERING
– HEART RATE MONITORS
• WEIGH SCALES
• BATTERY-POWERED INSTRUMENTS
• THERMOPILE MODULES
• HANDHELD TEST EQUIPMENT
• SENSOR SIGNAL CONDITIONING
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
2microPOWER is a trademark of Texas Instruments Incorporated.
3All other trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date. Copyright © 2008–2009, Texas Instruments Incorporated
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
1
2
3
5
4
V+
+In
V-
-In Out
OPA378
SC70-5
(TOPVIEW)
1
2
3
5
4
V+
-In
Out
V-
+In
OPA378
SOT23-5
(TOPVIEW)
1
2
3
4
8
7
6
5
V+
OutB
-InB
+InB
OutA
-InA
+InA
V-
A
B
OPA2378
SOT23-8
(TOPVIEW)
OPA378
OPA2378
SBOS417D –JANUARY 2008–REVISED OCTOBER 2009
www.ti.com
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
PACKAGE INFORMATION(1)
PRODUCT PACKAGE-LEAD PACKAGE DESIGNATOR PACKAGE MARKING
OPA378 SOT23-5 DBV OAZI
OPA378 SC70-5 DCK BTS
OPA2378 SOT23-8 DCN OCAI
(1) For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI
web site at www.ti.com.
ABSOLUTE MAXIMUM RATINGS(1)
Over operating free-air temperature range (unless otherwise noted). OPA378, OPA2378 UNIT
Supply Voltage, VS= (V+) – (V–) +7 V
Voltage(2) (V–) – 0.3 ≤VIN ≤(V+) + 0.3 V
Signal Input Terminals Current(2) ±10 mA
Output Short-Circuit(3) Continuous
Operating Temperature, TA–55 to +150 °C
Storage Temperature, TA–65 to +150 °C
Junction Temperature, TJ+150 °C
Human Body Model (HBM) 4000 V
ESD Ratings Charged Device Model (CDM) 1000 V
Machine Model (MM) 200 V
(1) Stresses above these ratings may cause permanent damage. Exposure to absolute maximum conditions for extended periods may
degrade device reliability. These are stress ratings only, and functional operation of the device at these or any other conditions beyond
those specified is not supported.
(2) Input terminals are diode-clamped to the power-supply rails. Input signals that can swing more than 0.3V beyond the supply rails should
be current limited to 10mA or less.
(3) Short-circuit to ground, one amplifier per package.
PIN CONFIGURATIONS
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OPA2378
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SBOS417D –JANUARY 2008–REVISED OCTOBER 2009
ELECTRICAL CHARACTERISTICS: VS= +2.2V to +5.5V
Boldface limits apply over the specified temperature range, TA= –40°C to +125°C.
At TA= +25°C, RL= 10kΩconnected to VS/2, VCM = VS/2, and VOUT = VS/2, unless otherwise noted.
OPA378, OPA2378
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
OFFSET VOLTAGE
Input Offset Voltage, OPA378 VOS VCM = V– 20 50 μV
vs Temperature dVOS/dT 0.1 0.25 μV/°C
Input Offset Voltage, OPA2378 20 70 µV
vs Temperature dVOS/dT -40°C to +125°C 0.25 0.4 µV/°C
–40°C to +85°C 0.15 0.25 µV/°C
vs Power Supply, OPA378 PSRR VCM = 0V, VS= +2.2V to +5.5V 1.5 5 μV/V
over Temperature VCM = 0V, VS= +2.2V to +5.5V 3 8 μV/V
vs Power Supply, OPA2378 VCM = 0V, VS= +2.2V to +5.5V 10 μV/V
over Temperature VCM = 0V, VS= +2.2V to +5.5V 3 13 μV/V
Channel Separation (Dual Version) At dc 135 dB
INPUT BIAS CURRENT
Input Bias Current, OPA378 IB±150 ±550 pA
Input Bias Current, OPA2378 ±150 ±670 pA
over Temperature, OPA378 and OPA2378 ±2 nA
Input Offset Current, OPA378 IOS ±0.3 ±1.1 nA
Input Offset Current, OPA2378 ±0.3 ±1.34 nA
NOISE
Input Voltage Noise enf = 0.1Hz to 10Hz, VS= +5.5V 0.4 μVPP
Input Voltage Noise Density enf = 1kHz 20 nV/√Hz
Input Current Noise inf = 10Hz 200 fA/√Hz
INPUT VOLTAGE RANGE
Common-Mode Voltage Range VCM (V–) – 0.05 (V+) + 0.05 V
Common-Mode Rejection Ratio CMRR (V–) – 0.05V < VCM < (V+) + 0.05V, VS= 5.5V 100 112 dB
(V–) – 0.05V < VCM < (V+) + 0.05V, VS= 2.2V 94 106 dB
over Temperature (V–) – 0.05V < VCM < (V+) + 0.05V, VS= 5.5V 96 dB
(V–) – 0.05V < VCM < (V+) + 0.05V, VS= 2.2V 90 dB
INPUT CAPACITANCE
Differential CIN 4 pF
Common-Mode 5 pF
OPEN-LOOP GAIN
Open-Loop Voltage Gain AOL 50mV < VO< (V+) – 50mV, RL= 100kΩ110 134 dB
100mV < VO< (V+) – 100mV, RL= 10kΩ110 130 dB
over Temperature 100mV < VO< (V+) – 100mV, RL= 10kΩ106 dB
FREQUENCY RESPONSE
Gain-Bandwidth Product GBW 900 kHz
Slew Rate SR G = +1 0.4 V/μs
Settling Time 0.1% tSVS= 5.5V, 2V Step, G = +1 7 μs
Settling Time 0.01% tSVS= 5.5V, 2V Step, G = +1 9 μs
Overload Recovery Time VIN × Gain > VS4μs
THD + Noise THD + N VS= 5V, VO= 3VPP, G = +1, f = 1kHz 0.003 %
Copyright © 2008–2009, Texas Instruments Incorporated Submit Documentation Feedback 3
Product Folder Link(s): OPA378 OPA2378
OPA378
OPA2378
SBOS417D –JANUARY 2008–REVISED OCTOBER 2009
www.ti.com
ELECTRICAL CHARACTERISTICS: VS= +2.2V to +5.5V (continued)
Boldface limits apply over the specified temperature range, TA= –40°C to +125°C.
At TA= +25°C, RL= 10kΩconnected to VS/2, VCM = VS/2, and VOUT = VS/2, unless otherwise noted.
OPA378, OPA2378
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
OUTPUT
Voltage Output Swing from Rail, VORL= 10kΩ6 8 mV
OPA378
over Temperature RL= 10kΩ8 13 mV
Voltage Output Swing from Rail, VORL= 10kΩ6 10 mV
OPA2378
over Temperature RL= 10kΩ8 15 mV
Voltage Output Swing from Rail RL= 100kΩ0.7 2 mV
over Temperature RL= 100kΩ3 mV
Short-Circuit Current ISC ±30 mA
Capacitive Load Drive CLOAD See Figure 18 pF
Open-Loop Output Impedance ZOSee Figure 23 Ω
POWER SUPPLY
Specified Voltage Range VS2.2 5.5 V
Quiescent Current (per Amplifier) IQIO= 0mA, VS= +5.5V 125 150 μA
over Temperature 165 μA
TEMPERATURE RANGE
Specified Range –40 +125 °C
Operating Range –55 +150 °C
Thermal Resistance θJA °C/W
SOT23-5 200 °C/W
SC70-5 250 °C/W
SOT23-8 100 °C/W
4Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated
Product Folder Link(s): OPA378 OPA2378
100nV/div
Time(1s/div)
1
VoltageNoiseDensity(nV/ )ÖHz
CurrentNoise(fA/ )ÖHz
Frequency(Hz)
10 100 1k 10k
1k
100
10
1
CurrentNoise
VoltageNoise
ContinueswithNo1/f(flicker)Noise
Population
-50
OffsetVoltage( V)m
-40
-30
-20
-10
0
10
20
30
40
50
-45
45
35
25
15
5
-5
-15
-25
-35
V =5.5V
S
Population
|OffsetVoltageDrift|( V/ C)m °
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.10
0.12
0.14
0.16
0.18
0.20
0.22
0.24
0.11
0.13
0.15
0.17
0.19
0.21
0.23
0.25
V =5.5V
S
OPA378
OPA2378
www.ti.com
SBOS417D –JANUARY 2008–REVISED OCTOBER 2009
TYPICAL CHARACTERISTICS
At TA= +25°C, RL= 10kΩ, VS= +5.5V and VOUT = VS/2, unless otherwise noted.
INPUT CURRENT AND VOLTAGE NOISE
0.1Hz TO 10Hz NOISE SPECTRAL DENSITY vs FREQUENCY
Figure 1. Figure 2.
OFFSET VOLTAGE
PRODUCTION DISTRIBUTION OFFSET VOLTAGE DRIFT DISTRIBUTION
Figure 3. Figure 4.
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Product Folder Link(s): OPA378 OPA2378
-75
OffsetVoltage( V)m
Temperature( C)°
0-50 50 100 125 150
80
60
40
20
0
20
40
60
80
-
-
-
-
-25 25 75
1
PSRR(dB)
Frequency(Hz)
10 100 1k 100k 1M
120
100
80
60
40
20
0
+PSRR
-PSRR
10k
-75
A (dB)
OL
Temperature( C)°
0-25 25 50 10075 125 150
150
145
140
135
130
125
120
115
110
105
100
-50
R =100kW
L
R =10kW
L
R =5kW
L
-75
PSRR,CMRR(dB)
Temperature( C)°
0-25 25 50 10075 125 150
140
130
120
110
100
90
80
-50
PSRR
V =5.5V
S
CMRR
V =5.5V
S
CMRR
V =2.2V
S
10
CMRR(dB)
Frequency(Hz)
100 1k 10k 100k 1M
120
100
80
60
40
20
0
OPA378
OPA2378
SBOS417D –JANUARY 2008–REVISED OCTOBER 2009
www.ti.com
TYPICAL CHARACTERISTICS (continued)
At TA= +25°C, RL= 10kΩ, VS= +5.5V and VOUT = VS/2, unless otherwise noted.
POWER-SUPPLY REJECTION RATIO
OFFSET VOLTAGE vs TEMPERATURE vs FREQUENCY
Figure 5. Figure 6.
OPEN-LOOP GAIN AND PHASE OPEN-LOOP GAIN
vs FREQUENCY vs TEMPERATURE
Figure 7. Figure 8.
COMMON-MODE REJECTION RATIO COMMON-MODE REJECTION RATIO AND
vs FREQUENCY POWER-SUPPLY REJECTION RATIO vs TEMPERATURE
Figure 9. Figure 10.
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Product Folder Link(s): OPA378 OPA2378
InputBiasCurrent(pA)
2000
1500
1000
500
0
500
1000
1500
2000
-
-
-
-
-75
Temperature(°C)
0-25 25 50 10075 125 150-50
InputBiasCurrent(pA)
InputCommon-ModeVoltage(V)
1.0
400
300
200
100
0
100
200
300
400
-
-
-
-
2.0 3.0 4.0 5.0-0.5
-IB
+IB
5.50 0.5 1.5 2.5 3.5 4.5
QuiescentCurrent( A)m
V (V)
S
2.0 5.5
200
175
150
125
100
75
2.5 3.0 3.5 4.0 4.5 5.0
QuiescentCurrent( A)m
Temperature(°C)
-75 -25 150
200
175
150
125
100
75
0 25 50 75 100 125-50
OutputSwing(V)
OutputCurrent(mA)
0 2 20
3
2
1
0
-1
-2
-3
4 6 8 10 12 14 16 18
-40°C
+25 C°
+125 C°
-40°C
+25 C°
+125 C°
+125 C°+25 C°
-40°C
V = 1.1
S±
V+=+2.75
V = 2.75- -
OutputVoltage(V)
Frequency(Hz)
1k 10k 1M100k 10M
6
5
4
3
2
1
0
V =5.5V
S
V =2.2V
S
OPA378
OPA2378
www.ti.com
SBOS417D –JANUARY 2008–REVISED OCTOBER 2009
TYPICAL CHARACTERISTICS (continued)
At TA= +25°C, RL= 10kΩ, VS= +5.5V and VOUT = VS/2, unless otherwise noted.
INPUT BIAS CURRENT INPUT BIAS CURRENT
vs INPUT COMMON-MODE VOLTAGE vs TEMPERATURE
Figure 11. Figure 12.
QUIESCENT CURRENT QUIESCENT CURRENT
vs SUPPLY VOLTAGE vs TEMPERATURE
Figure 13. Figure 14.
OUTPUT VOLTAGE SWING MAXIMUM OUTPUT VOLTAGE
vs OUTPUT CURRENT vs FREQUENCY
Figure 15. Figure 16.
Copyright © 2008–2009, Texas Instruments Incorporated Submit Documentation Feedback 7
Product Folder Link(s): OPA378 OPA2378
10
THD+N(%)
Frequency(Hz)
100 1k 10k
1
0.1
0.01
0.001
0.0001
1
Overshoot(%)
LoadCapacitance(pF)
10 100 1k
60
50
40
30
20
10
0
Gain=+1V/V, 1V/V-
R=10kW
Gain= 1V/V-
R=5kW
1V/div
0
2V/div
0
Time(10 s/div)m
10kW
1kW
OPA378
+2.5V
-2.5V
RL
Output
Input
Time(4 s/div)m
1V/div
0
2V/div
0
Output
Input
10kW
1kW
OPA378
+2.5V
-2.5V
RL
Voltage(1V/div)
Time(20 s/div)m
V = 2.75V±
S
VIN VOUT
OutputVoltage(10mV/div)
Time(5 s/div)m
G=+1
OPA378
OPA2378
SBOS417D –JANUARY 2008–REVISED OCTOBER 2009
www.ti.com
TYPICAL CHARACTERISTICS (continued)
At TA= +25°C, RL= 10kΩ, VS= +5.5V and VOUT = VS/2, unless otherwise noted.
TOTAL HARMONIC DISTORTION + NOISE SMALL-SIGNAL OVERSHOOT
vs FREQUENCY vs LOAD CAPACITANCE
Figure 17. Figure 18.
POSITIVE OVER-VOLTAGE RECOVERY NEGATIVE OVER-VOLTAGE RECOVERY
Figure 19. Figure 20.
SMALL-SIGNAL STEP RESPONSE LARGE-SIGNAL STEP RESPONSE
Figure 21. Figure 22.
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OutputImpedance( )W
10k
1k
100
10
1
0.1
1
Frequency(Hz)
1k100 10k 100k 1M10
I =0A
O
I =400 Am
O
I =2mA
O
InputBiasCurrent( A)m
50
40
30
20
10
0
10
20
30
40
50
-
-
-
-
-
-1V
InputDifferentialVoltage(mV)
-400-600 -200 0 400200 600 1V-800 800
NormalOperatingRange
(seethe
sectioninthe
ApplicationsInformation)
InputDifferential
Voltage
Over-DrivenConditionOver-DrivenCondition
1k
Overshoot(%)
Frequency(Hz)
10k 100k 1G
-160
140
120
100
80
60
40
20
0
-
-
-
-
-
-
-
1M 10M 100M
OPA378
OPA2378
www.ti.com
SBOS417D –JANUARY 2008–REVISED OCTOBER 2009
TYPICAL CHARACTERISTICS (continued)
At TA= +25°C, RL= 10kΩ, VS= +5.5V and VOUT = VS/2, unless otherwise noted.
INPUT BIAS CURRENT vs
OPEN-LOOP OUTPUT IMPEDANCE vs FREQUENCY INPUT DIFFERENTIAL VOLTAGE
Figure 23. Figure 24.
OPA2378 CHANNEL SEPARATION
Figure 25.
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-3.0
V ( V)m
OS
V (V)
CM
-2.0-2.5 -1.5 -1.0 -0.5 2.0
50
40
30
20
10
0
10
20
30
40
50
-
-
-
-
-
0 0.5 1.0 1.5 2.5 3.0
V = 2.75V
10TypicalUnitsShown
±
S
5kW
OPA378
10mAmax
+5V
VIN
VOUT
IOVERLOAD
Current-limitingresistor
requiredifinputvoltage
exceedssupplyrailsby
³0.5V.
OPA378
OPA2378
SBOS417D –JANUARY 2008–REVISED OCTOBER 2009
www.ti.com
APPLICATIONS INFORMATION
The OPA378 and OPA2378 are unity-gain stable,
precision operational amplifiers that are free from
phase reversal. The use of proprietary Zerø-Drift
circuitry gives the benefit of low input offset voltage
over time and temperature as well as lowering the 1/f
noise component. This design provides the
optimization of gain, noise, and power, making the
OPA378 series one of the best performers in this
bandwidth range. As a result of the high PSRR, this
device works well in applications that run directly from
battery power without regulation. They are optimized
for low-voltage, single-supply operation. These
miniature, high-precision, low quiescent current
amplifiers offer high-impedance inputs that have a
common-mode range 100mV beyond the supplies,
excellent CMRR, and a rail-to-rail output that swings
within 10mV of the supplies. This design results in Figure 26. Offset Voltage versus Common-Mode
superior performance for driving analog-to-digital Voltage
converters (ADCs) without degradation of differential
linearity. Normally, input bias current is about 150pA; however,
input voltages exceeding the power supplies can
OPERATING VOLTAGE cause excessive current to flow into or out of the
input pins. Momentary voltages greater than the
The OPA378 and OPA2378 can be used with single power supply can be tolerated if the input current is
or dual supplies from an operating range of VS=limited to 10mA. This limitation is easily accomplished
+2.2V (±1.1V) and up to VS= +5.5V (±2.75V). This with an input resistor, as Figure 27 shows.
device does not require symmetrical supplies, only a
differential supply voltage of 2.2V to 5.5V. A
power-supply rejection ratio of 1.5μV/V (typical)
ensures that the device functions with an unregulated
battery source. Supply voltages higher than +7V can
permanently damage the device; see the Absolute
Maximum Ratings table. Key parameters are assured
over the specified temperature range, TA= –40°C to
+125°C. Parameters that vary over the supply voltage
or temperature range are shown in the Typical
Characteristics section of this data sheet.
INPUT VOLTAGE Figure 27. Input Current Protection
The OPA378 and OPA2378 input common-mode
voltage range extends 0.05V beyond the supply rails.
The OPA378 achieves a common-mode rejection
ratio of 112dB (typical) over the common-mode
voltage range. Figure 26 shows the variation of offset
voltage over the entire specified common-mode
range for 10 typical units.
10 Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated
Product Folder Link(s): OPA378 OPA2378
CORE
-In
+In
Clamp
1.5kW
1.5kW
1k
FilterResponse(dB)
Frequency(Hz)
100k10k 1M 10M 100M 1G
0
10
20
30
40
-
-
-
-
f =25MHzwithParasitics
OverTemperature
29dBat800MHz-
C
OPA378
OPA2378
www.ti.com
SBOS417D –JANUARY 2008–REVISED OCTOBER 2009
INPUT DIFFERENTIAL VOLTAGE OPA378 operational amplifier family incorporates an
internal input low-pass filter that reduces the amplifier
The typical input bias current of the OPA378 during response to EMI. Both common-mode and
normal operation is approximately 150pA. In differential-mode filtering are provided by the input
over-driven conditions, the bias current can increase filter. The filter is designed for a cutoff frequency of
significantly (see Figure 24). The most common approximately 25MHz (–3dB), with a roll-off of 20dB
cause of an over-driven condition occurs when the op per decade. Figure 29 shows the EMI filter.
amp is outside of the linear range of operation. When
the output of the op amp is driven to one of the
supply rails the feedback loop requirements cannot
be satisfied and a differential input voltage develops
across the input pins. This differential input voltage
results in activation of parasitic diodes inside the front
end input chopping switches that combine with 1.5kΩ
EMI filter resistors to create the equivalent circuit
shown in Figure 28.
Figure 28. Equivalent Input Circuit Figure 29. EMI Filter
INTERNAL OFFSET CORRECTION GENERAL LAYOUT GUIDELINES
The OPA378 and OPA2378 family of op amps use an
auto-calibration technique with a time-continuous Attention to good layout practices is always
350kHz op amp in the signal path. This amplifier is recommended. Keep traces short and, when
zero-corrected every 3μs using a proprietary possible, use a printed circuit board (PCB) ground
technique. Upon power-up, the amplifier requires plane with surface-mount components placed as
approximately 100μs to achieve specified VOS close to the device pins as possible. Place a 0.1μF
accuracy. This architecture has no aliasing or flicker capacitor closely across the supply pins. These
noise. guidelines should be applied throughout the analog
circuit to improve performance.
NOISE For lowest offset voltage and precision performance,
The OPA378 series of op amps have excellent circuit layout and mechanical conditions should be
distortion characteristics. Total harmonic distortion + optimized. Avoid temperature gradients that create
noise is below 0.003% (G = +1, VO= 3VRMS, and f = thermoelectric (Seebeck) effects in the thermocouple
1kHz, with a 10kΩload). Design of low-noise op amp junctions formed from connecting dissimilar
circuits requires careful consideration of a variety of conductors. These thermally-generated potentials can
possible noise contributors: noise from the signal be made to cancel by assuring they are equal on
source, noise generated in the op amp, and noise both input terminals. Other layout and design
from the feedback network resistors. The total noise considerations include:
of the circuit is the root-sum-square combination of all • Use low thermoelectric-coefficient conditions
the noise components. (avoid dissimilar metals).
• Thermally isolate components from power
EMI SUSCEPTIBILITY AND INPUT FILTERING supplies or other heat sources.
Operational amplifiers vary in their susceptibility to • Shield op amp and input circuitry from air
electromagnetic interference (EMI). If conducted EMI currents, such as cooling fans.
enters the operational amplifier, the dc offset Following these guidelines reduces the likelihood of
observed at the amplifier output may shift from its junctions being at different temperatures, which can
nominal value while the EMI is present. This shift is a cause thermoelectric voltages of 0.1μV/°C or higher,
result of signal rectification associated with the depending on materials used.
internal semiconductor junctions. While all operational
amplifier pin functions can be affected by EMI, the
input pins are likely to be the most susceptible. The
Copyright © 2008–2009, Texas Instruments Incorporated Submit Documentation Feedback 11
Product Folder Link(s): OPA378 OPA2378
RF
Op-Amp
Core
RI
RL
V(1)
IN
ID
-In
Out
+In
ESDCurrent-
SteeringDiodes
Edge-TriggeredESD
AbsorptionCircuit
+VS
+V
-V
-VS
OPA378
ESD
ESD
ESD
ESD
V+
V-
OPA378
OPA2378
SBOS417D –JANUARY 2008–REVISED OCTOBER 2009
www.ti.com
ELECTRICAL OVERSTRESS It is helpful to have a good understanding of this
basic ESD circuitry and its relevance to an electrical
Designers often ask questions about the capability of overstress event. Figure 30 shows the ESD circuits
an operational amplifier to withstand electrical contained in the OPA378 (indicated by the dashed
overstress. These questions tend to focus on the line area). The ESD protection circuitry involves
device inputs, but may involve the supply voltage pins several current-steering diodes connected from the
or even the output pin. Each of these different pin input and output pins and routed back to the internal
functions have electrical stress limits determined by power-supply lines, where they meet at an absorption
the voltage breakdown characteristics of the device internal to the operational amplifier. This
particular semiconductor fabrication process and protection circuitry is intended to remain inactive
specific circuits connected to the pin. Additionally, during normal circuit operation.
internal electrostatic discharge (ESD) protection is
built into these circuits to protect them from
accidental ESD events both before and during
product assembly.
(1) VIN = +VS+ 500mV.
Figure 30. Equivalent Internal ESD Circuitry and Its Relation to a Typical Circuit Application
12 Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated
Product Folder Link(s): OPA378 OPA2378
R1
VEX
VOUT
VREF
R1
OPA378
R
R
R R
+5V
OPA378
OPA2378
www.ti.com
SBOS417D –JANUARY 2008–REVISED OCTOBER 2009
An ESD event produces a short duration, Another common question involves what happens to
high-voltage pulse that is transformed into a short the amplifier if an input signal is applied to the input
duration, high-current pulse as it discharges through while the power supplies +VSand/or –VSare at 0V.
a semiconductor device. The ESD protection circuits Again, it depends on the supply characteristic while at
are designed to provide a current path around the 0V, or at a level below the input signal amplitude. If
operational amplifier core to prevent it from being the supplies appear as high impedance, then the
damaged. The energy absorbed by the protection operational amplifier supply current may be supplied
circuitry is then dissipated as heat. by the input source via the current steering diodes.
This state is not a normal bias condition; the amplifier
When an ESD voltage develops across two or more most likely will not operate normally. If the supplies
of the amplifier device pins, current flows through one are low impedance, then the current through the
or more of the steering diodes. Depending on the steering diodes can become quite high. The current
path that the current takes, the absorption device level depends on the ability of the input source to
may activate. The absorption device has a trigger, or deliver current, and any resistance in the input path.
threshold voltage, that is above the normal operating
voltage of the OPA378 but below the device APPLICATION IDEAS
breakdown voltage level. Once this threshold is
exceeded, the absorption device quickly activates Figure 31 shows the basic configuration for a bridge
and clamps the voltage across the supply rails to a amplifier.
safe level. A low-side current shunt monitor is shown in
When the operational amplifier connects into a circuit Figure 32. RNare optional resistors used to isolate
such as that illustrated in Figure 30, the ESD the ADS8325 from the noise of the digital two-wire
protection components are intended to remain bus. Because the ADS8325 is a 16-bit converter, a
inactive and not become involved in the application precise reference is essential for maximum accuracy.
circuit operation. However, circumstances may arise If absolute accuracy is not required, and the 5V
where an applied voltage exceeds the operating power supply is sufficiently stable, the REF3330 may
voltage range of a given pin. Should this condition be omitted.
occur, there is a risk that some of the internal ESD Figure 33 shows a high-side current monitor. The
protection circuits may be biased on, and conduct load current develops a voltage drop across RSHUNT.
current. Any such current flow occurs through The noninverting input monitors this voltage and is
steering diode paths and rarely involves the duplicated on the inverting input. RGthen has the
absorption device. same voltage drop as RSHUNT. RGcan be sized to
Figure 30 depicts a specific example where the input provide whatever current is most convenient to the
voltage, VIN, exceeds the positive supply voltage designer based on design constraints. The current
(+VS) by 300mV or more. Much of what happens in from RGthen flows through the MOSFET and to
the circuit depends on the supply characteristics. If resistor RL, creating a voltage that can be read. Note
+VScan sink the current, one of the upper input that RLand RGset the voltage gain of the circuit.
steering diodes conducts and directs current to +VS.The supply voltage for the op amp is derived from the
Excessively high current levels can flow with zener diode. For the OPA378 VSmust be between
increasingly higher VIN. As a result, the datasheet 2.2V and 5.5V. Two possible methods to bias the
specifications recommend that applications limit the zener are shown in the circuit of Figure 33: the
input current to 10mA. customary resistor bias and the current monitor. The
If the supply is not capable of sinking the current, VIN current monitor biasing achieves the lowest possible
may begin sourcing current to the operational voltage. Resistor R1and the diode on the
amplifier, and then take over as the source of positive noninverting input provide short-circuit protection.
supply voltage. The danger in this case is that the
voltage can rise to levels that exceed the operational
amplifier absolute maximum ratings. In extreme but
rare cases, the absorption device triggers on while
+VSand –VSare applied. If this event happens, a
direct current path is established between the +VS
and –VSsupplies. The power dissipation of the
absorption device is quickly exceeded, and the
extreme internal heating destroys the operational
amplifier.
Figure 31. Single Op Amp Bridge Amplifier
Copyright © 2008–2009, Texas Instruments Incorporated Submit Documentation Feedback 13
Product Folder Link(s): OPA378 OPA2378
OPA378
ADS1100
Load
V
I C
2
R1
4.99kW
R3
4.99kW
R4
48.7kW
R2
49.9kW
+5V
3V
REF3330
R7
1.18kW
RSHUNT
1W
R6
71.5kWRN
56W
RN
56W
(PGAGain=4)
FS=3.0V
StrayGround-LoopResistance
ILOAD
R
600
S
W
C
1.2nF
1
OPA378
Output
RSHUNT
Load
V+
V+
RG
RL
R(2)
1
10kW
RBIAS
+5V
zener(1)
Twozener
biasingmethods
areshown.(3)
MOSFETratedto
stand-offsupplyvoltage
suchasBSS84for
upto50V.
RSHUNT CBYPASS
OPA378
OPA2378
SBOS417D –JANUARY 2008–REVISED OCTOBER 2009
www.ti.com
NOTE: 1% resistors provide adequate common-mode rejection at small ground-loop errors.
Figure 32. Low-Side Current Monitor
(1) Zener rated for op amp supply capability (that is, 5.1V for the OPA378).
(2) Current-limiting resistor.
(3) Choose zener biasing resistor or dual NMOSFETs (2N7002, NTZD511ON, SM6K2T110).
Figure 33. High-Side Current Monitor
14 Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated
Product Folder Link(s): OPA378 OPA2378
+ +
+
- -
3.3V
0.1 Fm
+5V
ZeroAdj.
K-Type
Thermocouple
40.7 V/ Cm °
R7
549W
R8
150kW
R5
31.6kW
R1
6.04kW
R6
200W
+5V
0.1 Fm
R2
2.94kW
VO
R3
60.4W
R4
6.04kW
OPA378
D1
REF3333
0.1 Fm
10 Fm
OPA378
3V
1MW60kW100kW
1MWNTC
Thermistor
V1
-In
V2
+In
R1
R2
2
3
5
6
1
R2
OPA378
OPA378
INA152
VO
V =(1+2R /R
O 2 1 2 1
)(V V )-
OPA378
OPA2378
www.ti.com
SBOS417D –JANUARY 2008–REVISED OCTOBER 2009
Figure 34. Temperature Measurement
Figure 35. Thermistor Measurement
Figure 36. Precision Instrumentation Amplifier
Copyright © 2008–2009, Texas Instruments Incorporated Submit Documentation Feedback 15
Product Folder Link(s): OPA378 OPA2378
R1
100kW
1/2
OPA2378
RA
Inverted
VCM
+VS
INA321(1)
+VS
VOUT
+VS
+VS
+VS
OPA378
+VS
1/2VS
dc
3
21
4
5
6
G =1kV/V
TOT
G =5
INA
G =200
OPA
f =150Hz
LPF
f =0.5Hz
HPF
(providesacsignalcoupling)
V =+2.7Vto+5.5V
S
BW=0.5Hzto150Hz
f =0.5Hz
O
Wilson
VCENTRAL
(RA+LA+LL)/3
7
ac
1/2VS
R2
100kW
1/2
OPA2378
LL
+VS
R3
100kW
1/2
OPA2378
LA
R4
100kW
R9
20kW
R6
100kW
RL
+VS
+VS
1/2
OPA2378
1/2
OPA2378
1/2
OPA2378
C4
1.06nF
C3
1 Fm
R14
1MW
R12
5kW
R13
318kW
R7
100kW
R8
100kW
R10
1MW
C2
0.64 Fm
R11
1MW
C1
47pF
R5
390kW
OPA378
OPA2378
SBOS417D –JANUARY 2008–REVISED OCTOBER 2009
www.ti.com
(1) Other instrumentation amplifiers can be used, such as the INA326, which has lower noise but higher quiescent current.
Figure 37. Single-Supply, Very Low Power ECG Circuit
16 Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated
Product Folder Link(s): OPA378 OPA2378
OPA378
C
600pF
4
R
100kW
3
OPA378
C
110pF
7
R
100kW
5
C
470nF
6
C
10 Fm
5R4
10kW
R2
10kW
+5V
+5V
C
1 Fm
3
C
10 Fm
2
VBIAS2
VBIAS1
Mic
Output
Mic
Bias
C
33pF
1
Out
Gnd
DigitalStethoscope
MicrophoneOutput
Electret
Microphone
Element
with
InternalFET
2.2kW
OPA378
OPA2378
www.ti.com
SBOS417D –JANUARY 2008–REVISED OCTOBER 2009
Figure 38. Digital Stethoscope Circuit
Copyright © 2008–2009, Texas Instruments Incorporated Submit Documentation Feedback 17
Product Folder Link(s): OPA378 OPA2378
OPA378
OPA2378
SBOS417D –JANUARY 2008–REVISED OCTOBER 2009
www.ti.com
REVISION HISTORY
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision C (June 2009) to Revision D Page
• Changed OPA2378 orderable status to production data; updated references throughout document ................................. 1
• Changed first sentence of Description section ..................................................................................................................... 1
• Deleted footnote 2 from Package Information table ............................................................................................................. 2
• Added OPA2378 parameters to the Offset Voltage section of the Electrical Characteristics table ...................................... 3
• Deleted footnote 1 from Electrical Characteristics table ....................................................................................................... 3
• Added OPA378 to the Offset Voltage, Input Offset Voltage and vs Power Supply parameters of the Electrical
Characteristics table ............................................................................................................................................................. 3
• Added typical specification to the OPA378 Offset Voltage, Over Temperature parameter of the Electrical
Characteristics table ............................................................................................................................................................. 3
• Added Offset Voltage, Channel Separation parameter to the Electrical Characteristics table ............................................. 3
• Added OPA2378 parameters to the Input Bias Current section of the Electrical Characteristics table ............................... 3
• Added OPA378 to the Input Bias Current, Input Bias Current and Input Offset Current parameters of the Electrical
Characteristics table ............................................................................................................................................................. 3
• Added typical specification to the Input Bias Current, Input Offset Current, OPA378 parameter of the Electrical
Characteristics table ............................................................................................................................................................. 3
• Added OPA378 to the Output, Voltage Output Swing from Rail parameter of the Electrical Characteristics ...................... 4
• Added typical specification to the OPA378 Output, Over Temperature parameter of the Electrical Characteristics
table ...................................................................................................................................................................................... 4
• Added the OPA2378 Output, Voltage Output Swing from Rail and Over Temperature parameters to the Electrical
Characteristics table ............................................................................................................................................................. 4
• Updated Figure 18 ................................................................................................................................................................ 8
• Added Figure 25 ................................................................................................................................................................... 9
• Updated Figure 32 .............................................................................................................................................................. 14
• Updated Figure 33 and changed footnote 3 ....................................................................................................................... 14
18 Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated
Product Folder Link(s): OPA378 OPA2378
PACKAGING INFORMATION
Orderable Device Status (1) Package
Type Package
Drawing Pins Package
Qty Eco Plan (2) Lead/Ball Finish MSL Peak Temp (3)
OPA2378AIDCNR ACTIVE SOT-23 DCN 8 3000 Green (RoHS &
no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR
OPA2378AIDCNT ACTIVE SOT-23 DCN 8 250 Green (RoHS &
no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR
OPA378AIDBVR ACTIVE SOT-23 DBV 5 3000 Green (RoHS &
no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR
OPA378AIDBVT ACTIVE SOT-23 DBV 5 250 Green (RoHS &
no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR
OPA378AIDCKR ACTIVE SC70 DCK 5 3000 Green (RoHS &
no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR
OPA378AIDCKT ACTIVE SC70 DCK 5 250 Green (RoHS &
no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check
http://www.ti.com/productcontent for the latest availability information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and
package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS
compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame
retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)
(3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the
accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take
reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on
incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited
information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
to Customer on an annual basis.
PACKAGE OPTION ADDENDUM
www.ti.com 30-Oct-2009
Addendum-Page 1
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device Package
Type Package
Drawing Pins SPQ Reel
Diameter
(mm)
Reel
Width
W1 (mm)
A0
(mm) B0
(mm) K0
(mm) P1
(mm) W
(mm) Pin1
Quadrant
OPA2378AIDCNR SOT-23 DCN 8 3000 179.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3
OPA2378AIDCNT SOT-23 DCN 8 250 179.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3
OPA378AIDBVR SOT-23 DBV 5 3000 179.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3
OPA378AIDBVT SOT-23 DBV 5 250 179.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3
OPA378AIDCKR SC70 DCK 5 3000 179.0 8.4 2.2 2.5 1.2 4.0 8.0 Q3
OPA378AIDCKT SC70 DCK 5 250 179.0 8.4 2.2 2.5 1.2 4.0 8.0 Q3
PACKAGE MATERIALS INFORMATION
www.ti.com 28-Oct-2009
Pack Materials-Page 1
*All dimensions are nominal
Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)
OPA2378AIDCNR SOT-23 DCN 8 3000 195.0 200.0 45.0
OPA2378AIDCNT SOT-23 DCN 8 250 195.0 200.0 45.0
OPA378AIDBVR SOT-23 DBV 5 3000 195.0 200.0 45.0
OPA378AIDBVT SOT-23 DBV 5 250 195.0 200.0 45.0
OPA378AIDCKR SC70 DCK 5 3000 195.0 200.0 45.0
OPA378AIDCKT SC70 DCK 5 250 195.0 200.0 45.0
PACKAGE MATERIALS INFORMATION
www.ti.com 28-Oct-2009
Pack Materials-Page 2
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