General Description
The MAX44242 provides a combination of high voltage,
low noise, low input bias current in a dual channel and
features rail-to-rail at the output.
This dual amplifier operates over a wide supply voltage
range from a single 2.7V to 20V supply or split ±1.35V
to ±10V supplies and consumes only 1.2mA quiescent
supply current per channel.
The MAX44242 is a unity-gain stable amplifier with a
gain-bandwidth product of 10MHz. The device outputs
drive up to 200pF load capacitor without any external
isolation resistor compensation.
The MAX44242 is available in 8-pin SOT23 and µMAXM
packages and is rated for operation over the -40ºC to
+125ºC automotive temperature range.
Applications
●Chemical Sensor Interface
●Photodiode Sensor Interface
●Medical Pulse Oximetry
●Industrial: Process and Control
●Precision Instrumentation
Benets and Features
●2.7V to 20V Single Supply or ±1.35V to ±10V Dual
Supplies
●0.5pA (max) Input Bias Current
● 5nV/√Hz Input Voltage Noise
●10MHz Bandwidth
●8V/µs Slew Rate
●Rail-to-Rail Output
●Integrated EMI Filters
●1.2mA Supply Current per Amplifier
Ordering Information appears at end of data sheet.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
MAX44242
IN-
IN+
PHOTODIODE
REF
IN-
IN+
PHOTODIODE
VDD
REF
OUT
OUT
MAX44242 20V, Low Input Bias-Current,
Low-Noise, Dual Op Amplifier
19-6827 Rev 2; 4/18
Typical Application Circuit
EVALUATION KIT AVAILABLE
Supply Voltage (VDD to VSS) ................................-0.3V to +22V
All Other Pins ................................(VSS - 0.3V) to (VDD + 0.3V)
Short-Circuit Duration to VDD or VSS ...................................... 1s
Continuous Input Current (Any Pins) ...............................±20mA
Differential Input Voltage ...................................................... ±6V
Continuous Power Dissipation (TA = +70°C)
8-Pin SOT23 (derate 5.1mW/°C above +70°C) .......408.2mW
8-Pin µMAX (derate 4.5mW/°C above +70°C) ............362mW
Operating Temperature Range ......................... -40°C to +125°C
Junction Temperature ...................................................... +150°C
Storage Temperature Range ............................ -65°C to +150°C
Lead Temperature (soldering, 10s) ................................. +300°C
SOT23
Junction-to-AmbientThermalResistance(θJA) ........196°C/W
Junction-to-CaseThermalResistance(θJC) ...............70°C/W
μMAX
Junction-to-AmbientThermalResistance(θJA) ........221°C/W
Junction-to-CaseThermalResistance(θJC) ...............42°C/W
(Note 1)
(VDD = 10V, VSS = 0V, VIN+ = VIN- = VDD/2, RL=10kΩtoVDD/2, TA = -40°C to +125°C, unless otherwise noted. Typical values are
at TA = +25°C.) (Note 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
POWER SUPPLY
Supply Voltage Range VDD Guaranteed by PSRR 2.7 20 V
Power-Supply Rejection Ratio PSRR VDD = 2.7V to 20V,
VCM = 0V
TA = +25ºC 106 130 dB
-40ºC≤TA≤+125ºC 100
QuiescentCurrentPerAmplier IDD RLOAD=innity TA = +25ºC 1.2 1.6 mA
-40ºC≤TA≤+125ºC 1.8
Power-Up Time tON 20 µs
DC CHARACTERISTICS
Input Common-Mode Range VCM Guaranteed by CMRR test VSS - 0.05 V
DD
- 1.5 V
Common-Mode Rejection Ratio CMRR VCM = VSS - 0.05V
to VDD - 1.5V
TA = +25ºC 94 111 dB
-40ºC≤TA≤+125ºC 90
InputO󰀨setVoltage VOS
TA = +25ºC 50 600 µV
-40ºC≤TA≤+125ºC 800
InputO󰀨setVoltageDrift(Note3) TC VOS 0.25 2.5 µV/ºC
Input Bias Current (Note 3) IB
TA = +25ºC 0.02 0.5
pA-40ºC≤TA≤+85ºC 10
-40ºC≤TA≤+125ºC 50
MAX44242 20V, Low Input Bias-Current,
Low-Noise, Dual Op Amplier
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Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
Package Thermal Characteristics
Electrical Characteristics
(VDD = 10V, VSS = 0V, VIN+ = VIN- = VDD/2, RL=10kΩtoVDD/2, TA = -40°C to +125°C, unless otherwise noted. Typical values are
at TA = +25°C.) (Note 2)
Note 2: All devices are production tested at TA = +25°C. Specifications over temperature are guaranteed by design.
Note 3: Guaranteed by design.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
InputO󰀨setCurrent(Note3) IOS
TA = +25°C 0.04 0.5
pA-40°C≤TA≤+85°C 10
-40°C≤TA≤+125°C 25
Open Loop Gain AVOL 250mV≤VOUT≤
VDD - 250mV
TA = +25°C 134 145 dB
-40°C≤TA≤+125°C 129
Input Resistance RIN
Di󰀨erential 50 MΩ
Common mode 200
Output Short-Circuit Current To VDD or VSS Noncontinuous 95 mA
Output Voltage Low VOL VOUT - VSS
RLOAD=10kΩtoVDD/2 25 mV
RLOAD=2kΩtoVDD/2 85
Output Voltage High VOH VDD - VOUT
RLOAD=10kΩtoVDD/2 37 mV
RLOAD=2kΩtoVDD/2 135
AC CHARACTERISTICS
Input Voltage-Noise Density enf = 1kHz 5 nV/√Hz
Input Voltage Noise 0.1Hz≤f≤10Hz 1.6 µVP-P
Input Current-Noise Density INf = 1kHz 0.3 pA/√Hz
Input Capacitance CIN 4 pF
Gain-Bandwidth Product GBW 10 MHz
Phase Margin PM CLOAD = 20pF 60 deg
Slew Rate SR AV = 1V/V, VOUT = 2VP-P, 10% to 90% 8 V/µs
Capacitive Loading CLOAD No sustained oscillation, AV = 1V/V 200 pF
Total Harmonic Distortion Plus
Noise THD+N VOUT = 2VP-P,
AV = +1V/V
f = 1kHz
-124
dB
f = 20kHz
-100
EMI Rejection Ratio EMIRR VRF_PEAK = 100mV
f = 400MHz
35
dB
f = 900MHz
40
f = 1800MHz
50
f = 2400MHz
57
Settling Time To 0.01%, VOUT = 2V step, AV = -1V/V
1
µs
MAX44242 20V, Low Input Bias-Current,
Low-Noise, Dual Op Amplier
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Electrical Characteristics (continued)
(VDD = 10V, VSS = 0V, outputs have RL=10kΩtoVDD/2. TA=+25°C,unlessotherwisespecied.)
0
5
10
15
20
25
-600 -400 -200 0200 400 600
OCCURRENCE N (%)
INPUT OFFSET VOLTAGE DRIFT (nV/°C)
INPUT OFFSET VOLTAGE DRIFT HISTOGRAM
toc02
HISTOGRAM
900
1000
1100
1200
1300
-50 -25 025 50 75 100 125
150
SUPPLY CURRENT PER AMPLIFIER (
μA)
TEMPERATURE (°C)
SUPPLY CURRENT PER AMPLIFIER
vs. TEMPERATURE
toc03
VIN = VDD/2
NO LOAD
VDD = 2.7V
VDD = 5.5V
VDD = 10V
VDD = 15V
VDD = 20V
-140
-120
-100
-80
-60
-40
-20
0
20
-1 13579
INPUT OFFSET VOLTAGE (
μV)
INPUT COMMON-MODE VOLTAGE (V)
INPUT OFFSET VOLTAGE
vs. INPUT COMMON-MODE VOLTAGE
vs. TEMPERATURE toc04
VIN = VDD/2
10kΩTA= +125°C
TA= +85°C
TA= +25°C
TA= -40°C
-100
-50
0
50
100
150
200
250
300
0246810
INPUT BIAS CURRENT (pA)
INPUT COMMON-MODE VOLTAGE (V)
INPUT BIAS CURRENT
vs. INPUT COMMON-MODE VOLTAGE
vs. TEMPERATURE
toc05
TA= +125°C
TA= +105°C
TA= +85°C
TA= +25°C
0
20
40
60
80
100
120
140
-50 -25 025 50 75 100 125
COMMON-
MODE REJECTION RATIO (dB)
TEMPERATURE (°C)
COMMON-MODE REJECTION RATIO
vs. TEMPERATURE
toc06
0
2
4
6
8
10
12
14
16
-250 -200 -150 -100 -50 050 100 150 200 250
OCCURRENCE N (%)
INPUT OFFSET VOLTAGE (μV)
INPUT OFFSET VOLTAGE HISTOGRAM
toc01
HISTOGRAM
30
50
70
90
110
130
150
-50 -25 025 50 75 100 125
POWER-
SUPPLY REJECTION RATIO (dB)
TEMPERATURE (°C)
POWER-SUPPLY REJECTION RATIO
vs. TEMPERATURE
toc07
0
20
40
60
80
100
120
140
1100 10000 1000000
AC CMRR (dB)
FREQUENCY (Hz)
AC CMRR
vs. FREQUENCY
toc08
MAX44242 20V, Low Input Bias-Current,
Low-Noise, Dual Op Amplier
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Typical Operating Characteristics
(VDD = 10V, VSS = 0V, outputs have RL=10kΩtoVDD/2. TA=+25°C,unlessotherwisespecied.)
-30
-10
10
30
50
70
90
110
130
10 1,000 100,000 10,000,000
AVOL (dB)
FREQUENCY (Hz)
AVOL
vs. FREQUENCY toc10
-20
-15
-10
-5
0
5
10
10 1,000 100,000 10,000,000
SMALL-SIGNAL RESPONSE (dB)
FREQUENCY (Hz)
SMALL-SIGNAL RESPONSE
vs. FREQUENCY
toc11
100mVP-P
INPUT
-30
-25
-20
-15
-10
-5
0
5
10 1,000 100,000 10,000,000
LARGE-SIGNAL RESPONSE (dB)
FREQUENCY (Hz)
LARGE-SIGNAL RESPONSE
vs. FREQUENCY
toc12
2VP-P Input 0
5
10
15
20
25
30
35
40
10 100 1000 10000 100000
INPUT VOLTAGE
-NOISE DENSITY (nV/√Hz)
FREQUENCY (Hz)
INPUT VOLTAGE-NOISE DENSITY
vs. FREQUENCY toc13
0.1 Hz to 10 Hz PEAK TO PEAK NOISE
toc14
VOUTN
VINSIDE
VBACKUP
1μ V/div
en = 1.6μ VP-P
20
40
60
80
100
120
10 1,000 100,000 10,000,000
AC PSRR (dB)
FREQUENCY (Hz)
AC PSRR
vs. FREQUENCY
toc09
0
1
2
3
4
5
10 100 1000 10000
INPUT CURRENT
-NOISE DENSITY (pA/√Hz)
FREQUENCY (Hz)
INPUT CURRENT-NOISE DENSITY
vs. FREQUENCY
toc15
0
50
100
150
200
250
300
350
400
450
500
550
600
650
04812 16 20
OUTPUT SWING HIGH (mV)
OUTPUT SOURCE CURRENT (mA)
OUTPUT VOLTAGE HIGH (VDD - VOUT)
vs. OUTPUT SOURCE CURRENT
toc16
MAX44242 20V, Low Input Bias-Current,
Low-Noise, Dual Op Amplier
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Typical Operating Characteristics (continued)
(VDD = 10V, VSS = 0V, outputs have RL=10kΩtoVDD/2. TA=+25°C,unlessotherwisespecied.)
0
20
40
60
80
100
120
-50 -20 10 40 70 100 130
TEMPERATURE (°C)
OUTPUT VOLTAGE SWING HIGH
vs. TEMPERATURE
toc18
RL= 10kΩ
RL= 2kΩ
0
10
20
30
40
50
60
70
-50 -20 10 40 70 100
130
OUTPUT VOLTAGE SWING LOW V
OL (mV)
TEMPERATURE (°C)
OUTPUT VOLTAGE SWING LOW
vs. TEMPERATURE
toc19
RL= 2kΩ
RL= 10kΩ
SMALL-SIGNAL RESPONSE
vs. TIME
toc20
100nF
VOUTN
VINSIDE
VBACKUP
1μ s/div
VOUTN
VINSIDE
VBACKUP
50mV/div
50mV/div
VIN
VOUT
No LOAD
0.001
0.01
0.1
1
10
100
100 1000 10000 100000
RESISTIVE LOAD (kΩ)
CAPACITIVE LOAD (pF)
STABILITY
vs. CAPACITIVE LOAD AND
RESISTIVE LOAD
STABLE
toc22
UNSTABLE
LARGE-SIGNAL RESPONSE
vs. TIME
toc21
1μs/div
VOUTN
VINSIDE
VBACKUP
toc21
1μs/div
VOUTN
VINSIDE
VBACKUP
No LOAD
VIN
1V/div
VOUT
1V/div
0.01
0.1
1
10
100
100 1000 10000 100000
ISOLATION RESISTANCE R
ISO (Ω)
CAPACITIVE LOAD (pF)
STABILITY
vs. CAPACITIVE LOAD AND
ISOLATION RESISTOR toc23
STABLE
UNSTABLE
0
50
100
150
200
250
300
350
400
450
500
550
600
0 5 10 15 20 25
30
OUTPUT SWING LOW (mV)
OUTPUT SINK CURRENT (mA)
OUTPUT VOLTAGE LOW (VOUT)
vs. OUTPUT SINK CURRENT
toc17
MAX44242 20V, Low Input Bias-Current,
Low-Noise, Dual Op Amplier
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Typical Operating Characteristics (continued)
(VDD = 10V, VSS = 0V, outputs have RL=10kΩtoVDD/2. TA=+25°C,unlessotherwisespecied.)
0
20
40
60
80
100
10 100 1000 10000
EMI REJECTION RATIO (dB)
FREQUENCY (MHz)
EMIRR
vs. FREQUENCY toc29
-120
-100
-80
-60
-40
-20
0
0246810
TOTAL HARMONIC DISTORTION (dB)
FREQUENCY (Hz)
TOTAL HARMONIC DISTORTION
vs. INPUT FREQUENCY
vs. AMPLITUDE
1kHz INPUT
FREQUENCY
toc26
RLOAD = 10kΩ
20kHz INPUT
FREQUENCY
-120
-100
-80
-60
-40
-20
0
110 100 1000 10000 100000 1000000
CROSSTALK (dB)
FREQUENCY (Hz)
CROSSTALK
vs. FREQUENCY toc27
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10 100 1000 10000 100000
TOTAL HARMONIC DISTORTION (dB)
FREQUENCY (Hz)
TOTAL HARMONIC DISTORTION
vs. FREQUENCY
2VP-P INPUT
toc25
RLOAD = 600ΩRLOAD = 1kΩRLOAD = 10kΩ
MAX44242 20V, Low Input Bias-Current,
Low-Noise, Dual Op Amplier
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Typical Operating Characteristics (continued)
Detailed Description
Combining high input impedance, low input bias current,
wide bandwidth, and fast settling time, the MAX44242 is
an ideal amplifier for driving precision analog-to-digital
inputs and buffering digital-to-analog converter outputs.
Input Bias Current
The MAX44242 features a high-impedance CMOS input
stage and a special ESD structure that allows low input
bias current operation at low-input, common-mode volt-
ages. Low input bias current is useful when interfacing
with high-ohmic or capacitive sensors and is beneficial for
designing transimpedance amplifiers for photodiode sen-
sors. This makes the device ideal for ground-referenced
medical and industrial sensor applications.
Integrated EMI Filter
Electromagnetic interference (EMI) noise occurs at higher
frequency that results in malfunction or degradation of
electrical equipment.
The MAX44242 has an input EMI filter to avoid the output
from getting affected by radio frequency interference. The
EMI filter, composed of passive devices, presents signifi-
cant higher impedance to higher frequencies.
High Supply Voltage Range
The device features 1.2mA current consumption per
channel and a voltage supply range from either 2.7V to
20V single supply or ±1.35V to ±10V split supply.
PIN NAME FUNCTION
1 OUTA Channel A Output
2 INA- Channel A Negative Input
3 INA+ Channel A Positive Input
4 VSS Negative Supply Voltage. Connect VSS to ground if single supply is used.
5 INB+ Channel B Positive Input
6 INB- Channel B Negative Input
7 OUTB Channel B Output
8 VDD Positive Supply Voltage
8µMAX/SOT-23
TOP VIEW
MAX44242
V
SS
1
2
INA-
INA+
OUTA
3
4
INB-
INB+
8
7
V
DD
OUTB
6
5
+
MAX44242 20V, Low Input Bias-Current,
Low-Noise, Dual Op Amplier
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Pin Description
Pin Conguration
Typical Application Circuit
High-Impedance Sensor Application
High impedance sources like pH sensor, photodiodes in
applications require negligible input leakage currents to
the input transimpedance/buffer structure. The MAX44242
benefits with clean and precise signal conditioning due to
its input structure.
The device interfaces to both current-output sensors
(photodiodes) (Figure 1), and high-impedance voltage
sources (piezoelectric sensors). For current output sen-
sors, a transimpedance amplifier is the most noise-effi-
cient method for converting the input signal to a voltage.
High-value feedback resistors are commonly chosen to
create large gains, while feedback capacitors help stabi-
lize the amplifier by cancelling any poles introduced in the
feedback loop by the highly capacitive sensor or cabling.
A combination of low-current noise and low-voltage noise
is important for these applications. Take care to calibrate
out photodiode dark current if DC accuracy is important.
The high bandwidth and slew rate also allow AC signal
processing in certain medical photodiode sensor applica-
tions such as pulse-oximetry. For voltage-output sensors,
a noninverting amplifier is typically used to buffer and/or
apply a small gain to the input voltage signal. Due to the
extremely high impedance of the sensor output, a low
input bias current with minimal temperature variation is
very important for these applications.
Transimpedance Amplier
As shown in Figure 2, the noninverting pin is biased at 2V
with C2 added to bypass high-frequency noise. This bias
voltage to reverse biases the photodiode D1 at 2V which
is often enough to minimize the capacitance across the
junction. Hence, the reverse current (IR) produced by the
photodiode as light photons are incident on it, a propor-
tional voltage is produced at the output of the amplifier by
the given relation:
OUT R
V I R1= ×
The addition of C1 is to compensate for the instability
caused due to the additional capacitance at the input
(junction capacitance Cj and input capacitance of the op
amp CIN), which results in loss of phase margin. More
information about stabilizing the transimpedance amplifier
can be found in Application Note 5129: Stabilize Your
Transimpedance Amplifier.
Figure 1. High-Impedance Source/Sensor Preamp Application
D1
MAX44242
+5V
5V
C1
15nF
R1
100kΩ
R2
30kΩ
C2
10nF
R3
20kΩ
MAX44242 20V, Low Input Bias-Current,
Low-Noise, Dual Op Amplier
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+Denotes lead(Pb)-free/RoHS-compliant package.
PART TEMP RANGE PIN-
PACKAGE
TOP
MARK
MAX44242AKA+ -40ºC to +125ºC 8 SOT23 AETK
MAX44242AUA+ -40ºC to +125ºC 8 µMAX —
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
8 SOT23 K8+5 21-0078 90-0176
8 µMAX U8+1 21-0036 90-0092
MAX44242 20V, Low Input Bias-Current,
Low-Noise, Dual Op Amplier
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Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
Chip Information
PROCESS: BiCMOS
Ordering Information
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 12/13 Initial release —
1 11/15 Updated Pin Conguration diagram 8
2 4/18 Updated Typical Application Circuit 1
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
MAX44242 20V, Low Input Bias-Current,
Low-Noise, Dual Op Amplier
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Revision History
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